“Throwing the baby out with the bathwater” means carelessly getting rid of something valuable while trying to discard something unwanted. The phrase comes from a 16th-century German proverb“das Kind mit dem Bade ausschütten.”

Back then, families bathed in the same tub, one after the other, with the baby going last. By then, the water was so murky the joke was you might toss the baby out with the dirty water if you weren't paying attention.

The phrase made its way into English in the 1800s, notably through Thomas Carlyle, who used it to warn against overcorrecting and losing something worth keeping.