Well, if your astrological sign happens to be Gemini, then a name meaning "twin" would have a certain amount of significance in that area.
Eusebius says that the original Thomas -- the apostle -- was really named "Judah", and that he had just been given the nickname meaning "twin" in order to distinguish him from a couple of other Judahs.
I remember there was a character named "Tamsin" in Thomas Hardy's *Return of the Native*.
-- Nanaea