As we know (almah is the female form of (elem, "lad, young man". Because
the latter is NOT used to indicate whether we are dealing with a young
man, who had sexual intercourse or not; it might be correct to consider
this fact also with regard to (almah. It is used for young women,
regardless wether they are married or not.
Bethulah occurs already in the texts of Ugarit to denote the goddess
(Anatu, who did have intercourse with her husband, the god Ba(lu. So
this word did originally not have the specific meaning of "virgin"in
West-semitic languages.