> There's another one of those weird multinational differences: Andrea is my mom's name, so I always figure, "girl." Once I met a guy named Andreas.

Here in Italy, "Andrea" is a guy, "Andreina" is a girl ("Andreas", as far as I know, is a German guy). In fact, my name always causes some odd misunderstandings when I've to meet with English-speaking people (see my reply to Brunnen-G for a sample!).
At any rate, "Andrea" as a latin name comes from Greek "Andros", that means "man" (also think to all "andro-" prefixed words, especially in the medical jargon, that refer to male-related topics).

A big hug,
AP