Metaphor for a young attractive person but these days is more frequently used in the negative i.e. ‘no spring chicken’, meaning that persons so described are past their best. It dates in this sense from the early 20th century and the expression originated in America. It is preceded by earlier English expressions, ‘no longer a chicken’ or ‘past a chicken’, which date from the early 18th century but have largely fallen into disuse. Young chickens, born in spring, and anything from two to ten months old, were considered by farmers to be very tender and therefore commanded better prices and this literal usage goes back to the early 1700s.