Etymology of 'Having Kittens!'

I recently started to use the expression 'have kittens' quite often, as in 'his nieces would have kittens if they heard that'. 

I wondered about the origin of the phrase and what I discovered surprised me. 

It derives from the belief of some women in the Middle Ages that they had been cursed and were going to give birth to cats, something which naturally made them distraught.

“In medieval times it was believed that if a pregnant woman was in pain, she had been cursed by a witch and had kittens inside clawing at her belly. Witches, they believed, could control cats, and could eliminate the kittens. Since a woman believing she was going to give birth to a litter of kittens would become hysterical, the phrase has, over time, come to mean being in an angry panic.”

As they say (on social media) who knew?