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.
Southern Italian: 1. from a dialect word, cascio ‘cheese’ (Italian cacio), with the definite article lo, presumably a metonymic occupational nickname for a maker or seller of cheese. 2. according to some sources, from a possible Sicilian form of Lo Castro.