Leech An English and an Irish surname. Derived from the Middle English leche for ‘physician’. A similar derivation from the Gaelic liaigh. In Galway ó Laoghógh (more usually Logue) is so translated. In 1890 Leech was principally found in Dublin, and the estimated number of bearers was 1,570. In the United States Leach is the 686th most numerous surname with an estimated 46,750 bearers. In England and Wales in 1996 Leach was the 404th most numerous surname.