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.
English and Scottish: patronymic from the medieval personal name Nel or Neal, Anglo-Scandinavian forms of the Gaelic name Niall (see Neill). This was adopted by the Scandinavians in the form Njal and was introduced into northern England and East Anglia by them, rather than being taken directly from Gaelic.