John Stephen Conmee was rector at Clongowes from 1885 to 1891. Joyce includes him in his novel as a bright figure, a person who helps Stephen when he is abusively punished by Father Dolan.
He might be the source of Stephen's name. Conmee also appears as a character in Ulysses, where he gets his own stream-of-consciousness at the opening of "The Wandering Rocks." He also briefly appears in the "Circe" chapter of the same book.