What does You Old Bat mean and where does the saying come from?

Answer 1

Here's a guess. It could be related to the word "Batty" meaning crazed, insane or erratic. It comes from the term Bats in the Belfry because bats who lived in bell towers in Europe seem to fly erratically on occasions. "Old bat" is often used in the sentence "You crazy old bat." I suspect it was shortened to "Old Bat" because it is impolite to call someone crazy. It also seems to be reserved for women. I've heard people refer to an angry wife as the old bat as well as the old battle axe. In sum, I would suggest it is a less hurtful way of calling someone crazy either to their face or behind their back.

Answer 2

It could very well come from an indigenous term for mother in law.

As custom, son in laws and mother in laws were not to look or recognise each other....when the son was near the mother in law she would shield her face with a rug or blanket which resembled a bat at rest covered by its wings.

Answer 3

I thought it was "old girl" from the Yiddish word for girl as in "Bat Mitzvah." Just a guess, though.