Why are females called chicks?

Answer 1

Women have called themselves hens for several centuries. An all women's gathering has been called a hen party for at least two centuries. In that context, the term hen indicated both gender and informality. The term chick naturally became used for women not old enough to be called hens. Its usage came from the vernacular and appears in several languages such as the Spanish chicas for Senoritas. Unlike the word hen, the term chick does not seem to be one that women ever chose to apply to themselves.