Pronounciation
It's not uncommon for multiple languages to have extremely close, if not outright "stolen" name sets. However, despite this, not every language also has the same capability of sounds. Take Arabic and English as examples (or Farsi and English) -
There is a character called "khâf". In English, we'd have an extremely difficult time pulling off the "kh" (it's extremely harsh, in the back of the throat) sound. So, we'd end-up saying something more like "cough".
Odds are - this is one of the many "Thomas" names that floated around from around 2000 B.C. to 1000 AD.
Didymus
Tumas
Thomas
etc
(Source: The Indoeuropean Etymological Dictionary)