English, French, German, Dutch, Danish, and South Indian: from
the medieval personal name, of Biblical origin, from Aramaic
t’ōm’a, a byname meaning ‘twin’. It was borne by one of the
disciples of Christ, best known for his scepticism about
Christ's resurrection (John 20:24–29). The th- spelling is
organic, the initial letter of the name in the Greek New
Testament being a theta. The English pronunciation as t rather
than th- is the result of French influence from an early date.
In Britain the surname is widely distributed throughout the
country, but especially common in Wales and Cornwall. The
Ukrainian form is Choma. It is found as a personal name among
Christians in India, and in the U.S. is used as a family name
among families from southern India.