Why do we speak of someone 'having kittens'?

 

When we say 'she will have kittens if she finds out about this' we mean that someone will be terribly upset, almost to the point of hysteria.
At first sight there is no obvious connection between distraught human behaviour and giving birth to kittens. True, a panic-stricken or hysterical woman who happens to be pregnant might suffer a miscarriage as a result of the intense emotional distress, so suddenly giving birth as a result of panic is not hard to understand. But why kittens?
Why not puppies, or some other animal image?
To find the answer we have to turn the clock back to medieval times, when cats were thought of as the witch's familiars. If a pregnant woman was suffering agonizing pains, it was believed that she was bewitched and that she had kittens clawing at her inside her womb.
Because witches had control over cats, they could provide magical potions to destroy the litter, so that the wretched woman would not give birth to kittens. As late as the seventeenth century an excuse for obtaining an abortion was given in court as removing 'cats in the belly'. Since any woman believing herself to be bewitched and about to give birth to a litter of kittens would become hysterical with fear and disgust, it is easy to see how the phrase 'having kittens' has come to stand for a state of angry panic.