This comment sums it up
My roommate first mentioned the name
Beulah to me, and I've been finding it more and more in my law hypos as I study for the California Bar, so it prompted me to find this site.
I was hoping it wasn't actually from the Hebrew b'ula, but apparently it is. It really doesn't mean a married woman. I mean we hope she's married, but it just means a woman who's been around the block (not necessarily slutty, but it means a woman who's had sex), as opposed to a b'tula - virgin. It's used a lot in Jewish legal texts (g'mara / talmud) to mean an unmarried woman who is unchaste, for purposes of measuring dowry, or fitness for marrying the kohen gadol (High Priest), which is where I know it from better than y'shaya (
Isiah).
It is related to the word for husband - baal (or owner), but so is one of the Hebrew words for sex (b'ila, livol - to have sex).
How this got to be a name in English is beyond me.