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.
German (common in the north of Germany and around Hamburg): in some cases probably a habitational name from the city of Kiel in Schleswig-Holstein, but more likely a topographic name for someone living by a long narrow bay or area of sheltered water, from Middle Low German kil ‘wedge’, the word from which the city derives its name. Alternatively, it may be from the same word applied as a nickname to denote a crude person.