Thomas Sullivan

(male) New Testament name, borne by one of Christ's twelve apostles, referred to as ‘Thomas, called Didymus’ (John 11:16; 20:24). Didymos is the Greek word for ‘twin’, and the name is the Greek form of an Aramaic byname meaning ‘twin’. The given name has always been popular throughout Christendom, in part because St Thomas's doubts have made him seem a very human character.

Irish: reduced form of O’Sullivan, an Anglicized form of Gaelic Ó Súileabháin ‘descendant of Súileabhán’, a personal name composed of the elements súil ‘eye’ + dubh ‘black’, ‘dark’ + the diminutive suffix -án.