Thomas (and Tomas) is a common surname used by the British (primarily Welsh), French, German, Dutch, Danish, and South Indian (Nasrani).
It derives from the medieval personal name, of Biblical origin, from Aramaic t'om'a, a byname meaning 'twin'. It was borne by one of the disciples of Christ, best known for his skepticism about Christ's resurrection. The th- spelling in English results from the initial letter of the name in the Greek New Testament being a theta. The English pronunciation as t rather than a dental fricative 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. Thomas is the ninth most common surname in the United Kingdom. It is found as a personal name among Christians in India, and in the United States; it is also used as a family name among the Jewish Christian (Nasrani) families from Kerala, South India.
In the 1990 United States Census, Thomas was the twelfth most common surname, accounting for 0.3% of the population.