Pronounced "bay", ba is a name used as a term of endearment, usually for a person in a romantic and/or sexual relationship. Ba is a second generation abbreviation, being a shortened form of babe
which is itself, duh, a shortened form of baby
She says, "Babe, Check out the new Trentmoller remix of Modeselektor."
He says, "Aight, I will. Thanks, ba."