Enya is surely Eithna, and wasn't she a different goddess from Áine?

At one time anyway it was quite frequent for boys to have Mary as a second name in some Catholic countries - plenty of Jean-Marie's in France for example; and in Ireland one of the poets shot after the Easter Rising in 1916 was Joseph Mary Plunkett.

Tracy a boys name? That must be American. This side it's always a girl's name, a version of Teresa, though people don't normally think of it that way.

Abbreviations always tend to be unisex. Bill, Pat, Sam etc. - that's because the names behind them come in gender pairs, and shortening them takes away the distinctive ending.