Though no genealogies of this family survive, or indeed any, records of the name prior to those of the 15th century, there is no doubt but that Iarlaithe is as ancient a personal name as any in Ireland. The patron saint of Tuam in Co. Galway was named Iarlaithe ('Jarlath'). In the period when family names were beginning to come into use, an Iarlaithe was chieftain of Uaithne, a tribal territory on the borders of Limerick and Tipperary. Perhaps the family originated here. It is recorded that the O'BRIEN's invaded Owney in 1313 and slew many of its inhabitants and it may be that some members then fled to Desmond. Though the O'HERLIHY's of the 16th century and perhaps for long before that  had a close association with the church lands of Ballyvourney, there is no mention of them in the 14th century Pipe Roll of Cloyne.

Throughout the entire 15th century however, clerics of the name were prominent in the dioceses of both Cloyne and Cork. The following were among those listed:

1411: Gillebert  O HIARLAYTHE, a Canon of Cork   possibly the same man who died (prior to 1458) Prebendary of Killaspugmullane (northeast of Cork city).

1427: Donald  O HYARLATHY, a Clerk of the diocese of Cloyne.

1445: Maurice 0 HERLATHY, Clerk, rector of Ballynoe in the diocese of Cloyne.

1465: Donald 0 HIARLACHAIG, Canon of Cork.

1471: Donatus (Donnchadh) and Nicolaus O HYERLATHY, Priests of Cloyne diocese.

1479: Rinaldus YHERLATHY, de facto Vicar of Clondrohid.

1481: Maurice 0 HYERLAYDH, Prebendary of Inishkenny (Waterfall).

1484: Williarn 0 HIRLATHI,  Canon of Cloyne.

1485: Johannes O HYERLAHY Jnr,  appointed treasurer of Cork diocese in place of John O HYERLAHY the Elder. Although not yet ordained he was given a Canonry and the Prebend of Desertmore, in order that he might engage in the study of letters.

1487: Donatus O HERLEY, canon of Cork.

1496: John  HYERLACHY,  Dean of Cork.

In the early 16th century there was a noted Franciscan, Father David O'HIERLAITHY (died 1544), who was twice Provincial of his order. (It may perhaps, have been the same Fatherr David who was credited with the rebuilding of Bantry Friary in 1482.) Even after the Reformation in 1591, David (Juvenis) O'HEARLEY who was a Layman, held the Vicarage of Ballyvourney until deprived of it for his "manifest contumacy" (failure to obey orders - JH).

But the most celebrated cleric to bear the family name was the saintly Thomas O'HERLIHY who was appointed Bishop of ross in 1561. He is said to have been born in Kilmacabea Parish (Glandore-Leap area) though no doubt connected with the Ballyvourney O'HERLIHY's. The Barberini Acts state that he was a Canon of Cork while the Corsini Acts refer to him as Thomas HIERLLAHIUS de nobili genere ex utroque parente procreatus, vita et scientia idoneus. Six months after his con­secration, Bishop O'HERLIHY was in attendance at the Council of Trent, one of only three lrish Bishops who attended. On his return to Ireland he zealously promoted the decrees of the council until forced to take refuge on an island off the coast where he was arrested in 1571 by one of the O'SULLIVAN's and handed over to Sir John PERROTT. He was con­fined in the Tower of London along with Primate CREAGH, but rejected all pressures to make him renounce his religion until eventually his release was secured by Cormac MacCARTHY, Lord of Muskerry. Refusing to live in Cormac’s castle he built himself a small hut in Muskerry - ­tradition says at Carraig an Easpaig in Sleveen near Macroom -  where he continued to minister to the people until he died in 1579. His burial ­place is in Kilcrea Friary.

All of Muskerry was, of course, part of the MacCARTHY domain. An account of the Lord of Muskerry’s lands in 1600 lists "O'HERLIEY" as one of the "countries in Muskrye" (those with ecclesiastical con­nections). The family group then held ten or eleven ploughlands. The head of the family, "Daniell  O'HERLIHIE de Ballyworny, Gentleman,"  was in 1576 one of the jurors in an inquisition held after the death of Sir Donogh MacCARTHY,  Riabhach of Carbery. In a pardon granted to Cormac MacCARTHY of Blarney and his followers In 1573 we find the names of David óg CONNOGHER and Shane, Yeomen, sons of Da (ie David) O'HIERLYHY  of Ballyvickydy (Ballymakeery). Others par­doned in the Elizabethan Fiants were:

1577: Thady Mac Thomas O'HYERLYHY and John O'HYERLYHY of Ballyvourney, Yeomen. Shane MacDonald Y HIERLLITHE of Bally­vourney, Soldier, John 0'HERLEHEY ny BAGHLEY of Banduff (Parish ar. Clondrohid), Yeoman.

1579: Donald O'HIERLYHY of Ballyvourney, Yeoman.

1585: Thomas MacDavy Y HERLIHY of Ballyvourney, Kern.

1601: William O'HIERLIHIE of Ballyvourney, Shane MacRanell I HIRLEIGHEY of Ballyvourney. John MacDonell I YERLEGHY of Ballyvourney, Cnoghor O'HIERLIHIE of Dunbeacon, Husbandman, Cnoghor MacHurly HIERLIHIE of Dundirig (Dundareirke), John O'HIERLIHIE of Ballyowcane (? Ballyourane, Parish Caheragh): Teige and Donogh MacMorrice O'HIERLIHIE, Morrish FitzJohn O'HIERLIHIE, Thomas and John Mac Connoghor O'HIERLIHIE, Thomas MacTeige O'HIERLIHIE.

William oge MacWilliam MacTeige O'HIERLIHY of Ballyvourney, head of the family, died in 1614. An inquisition (taken in 1625) into his lands found that he had owned Shanacloon, Gortnafunshion, Gortnatubbrid, Murnaghbeg. Derrylahan, Cappagh and other townlands in the parish, but the heirs of Thadeus O'HIERLIHY  claimed Cappagh and Currinclogh (? Coomaclohy). In 1608 he had granted lands to Daniel Mac William O'HIERLIHY. This was presumably, the Daniel O'HIERLIHIE  alias O'HIERLIHIE of Ballyvourney, Gentleman, who died on 2 March 1637. He was described in his funeral entry, as eldest son and heir of William, eldest son and heir of Daniel, eldest son and heir of William, descended (presumably on the maternal side) from the house of O'DONOGHOW  More of Onaght Idonoghow, Co. Kerry. He had been twice married (to Gyles. daughter of Art O'LEARY of Carrignancelagh and to Síle, daughter of Maolmhuire O'MAHONY of Gurtinroe, Co. Kerry, Gentleman) and had twelve sons and twelve daughters. He was buried in the old church of Ballyvourney: The O'HERLIHY tomb was on the north side of the altar. His eldest son and heir William, married Ellen, daughter of Callaghan MacCARTHY of Claraghbeg (Parish  Drishane), Gentleman.

The Civil Survey makes it clear that in 1641 the heirs of Thadeus O'HIERLIHY, (David Mac Teige HURLIHY and Daniel oge HIERLIHY) held Cappagh West only (Cappagh East was held by Thomas O'HIERLIHY. William, the Chief of his Sept, held Inshynogugalin (? Inchamore) where he lived. as well as Slievereagh (which had on it "the foundation of the stump of a small castle" - perhaps the original family, home and a demolished mill), Shanacloon (mortgaged to Oliver HIERLIHY). Killeen. Derreenaling, Coumaclovane, Fohiribany (Fuhiry), Derrylahan, Gortyrahilly, Derrynasaggart, Gortnafunshion. Coolea. Gortnascarty, Coolavokig. Murnaghbeg and Gortnatubbrid. This comprised practically the whole of Ballyvourney parish, apart from a section in the east, which belonged to the MacCARTHY's.

As usual, the landowners of the Sept incurred outlawry in 1643 - William and John O'HIERLIGHY of Ballyvourney, Gentlemen, Thomas of Cappagh, Gentleman and Donnogh (? Daniel) oge, Gentleman. So when the war had ended, over 12,000 plantation acres of O'HERLIHY lands in Ballyvourney  were confiscated and set out under CROMWELL to John COLTHURST. Up to 1691 there remained a slight hope that the O'HERLIHY's  might recover their lands, a hope that was terminated by the Treaty of Limerick. A John HERRLOHY of Tuogeage (?), Co. Cork, Gentleman was attainted as a Jacobite supporter in 1691 and Captain Daniel O'HERLIHY served in Boisseleau's Infantry in King James' Army at the same period. Following the treaty the authorities in Dublin castle proscribed certain individuals in Cos. Cork and Kerry, threatening with imprisonment any who harboured them. Amongst the suspected harbourers were O'HIERLIHY of Ballyvourney, David Baccoh O'HIERLIHY and Daniel Mac William HIERLIHY.

Dáibhidh Bacach O'HIARLAITHE was a well-known local poet at whose house in Ballyvourney the "tÃigse" used to assemble. But he appears to have been ousted from there and forced to remove to Glenflesk, an event deplored by a fellow-poet:

"Is cás lìom cill bliláfar na dtriatha suilt
Gan fáilte ruim tháintibh dá dtrialladh ann
Ó tiománadh ár n-ardflath fá iarthar cnoc
Dáth geal mac Pádraig � Iarlaithe".

Dáibhidh had two sons who became Priests - An t-Athair Uilliam and An t-Athair Pádraig - and both were poets as well. Quite a number of O'HERLIHY's composed poems in Irish in the 18th century, several of them, no doubt in the Ballyvourney area where O'HERLIHY's must have remained on as tenants after the Cromwellian plantation though we have no evidence of this in the 1659 census from which returns for Muskerry are missing. The census in fact, does not list O'HERLIHY as a principal Irish surname in any of the Baronies of Co. Cork although there were twenty families of the name "O'HERLYHY and O'HELYHY" in the Barony of Connello, Co. Limerick.

An old man in Cork City in 1706 told Bishop Dive DOWNES that at one time he used to receive the Bishop's Rents for Bishops' BOYLE and SYNGE (who occupied the Sees of Cork, Cloyne and Ross between 1660 and 1678) and that he received Seven Pounds per annum chiefLy out of the twelve  ploughlands of Ballyvourney, from the HIERLIGHY's during all that time.

John RICHARDSON in The Great Folly, Superstition and Idolatry of Pilgrimages in Ireland (1727) wrote thus of the much-venerated oaken statue of St. Gobnait in Ballyvourney:

"The image is kept by one of the family of the O'HERLIHY's and when anyone is sick of the Small-Pox, they send for it and sacrifice a sheep to it and wrap the skin about the sick person, and the family eat the sheep. But this hath now much lost its Reputation, because two of the O'HERLIHY's died lately of the Small Pox."

The O'HERLIHY's continued as guardians of the statue until 1843 when the hereditary representative on the female side, an O'BRIEN of Dunmanway, fearing for the safety of the statue, handed it over to the Parish Priest of Ballyvourney where it is still resorted to for cures.

In the mid-19th century on the COLTHURST estate (which was the old O'HERLIHY estate) there were five O'HERLIHY tenant-farmers while several others of the name lived in the parish, including the schoolmaster John O'HERLIHY who even before the founding of the National School system taught 68 scholars aided by a Twenty Pound  subscription from Sir Nicholas COLTHURST. Even today, Ballyvourney is still redolent of the family name. One of the traditional "stations" in the Round performed there is the "Priest's Tomb" at the right corner of the east gable of the ruined church, the burial place of Father O'HERLIHY. The graveyard also contains one of the very few mid-19th century gravestones to bear an inscription in Irish, as follows:

Uam adhlaicthe Ui Iarfhlaithe
taiseach tuatha Baile Mhuirne
Or f anm na treibhe.
Or f anm Seain mic Tadhg

do ecc san mbl. 1864

(The burial-place of O'HERLIHYLay Chief of Ballyvourney. Pray, for the souls of the Sept. Pray for the soul of Seán son of Tadhg who died in the year 1864.)