Didymus is the Greek word for "twin" and Thomas is from a Semitic word,either Hebrew or Aramaic, or Syriac,which are all three similar languages, "Thomas" would look like in "twin" in those.

低土马就是希腊语的“双生子“,“多马“来源于闪语，希伯来语或亚兰语，或者叙利亚语，这三种都是很相似的语言，“多马“在这些语言中也有“双生“的意思。

youdao