I know the meaning, but wanted to know the origin of the phrase.
Wiktionary says it originated in Shakespeare's MacBeth:
Ro. Wife, Children, Seruants, all that could be found. […]
Macd. […] All my pretty ones?
Did you ſay All? Oh Hell-Kite! All?
What, All my pretty Chickens, and their Damme
At one fell swoope?