"to pull a pair of bell-bottoms on"
Bell-bottoms, 1969-style
Public DomainBell-bottoms, 1969-style - Credit: Jeanne Boleyn, Wikimedia Commons

Mid-18th Century British sailors wearing bell-bottoms
Public DomainMid-18th Century British sailors wearing bell-bottoms - Credit: George Thomas (1854)
Bell-bottoms are trousers which flare out very widely from the knee downward.

They were traditionally worn as part of sailors' uniforms, but became fashionable for both men and women during the 1960s and 70s. Subsequently, they came to be viewed as symbols of the hippie era, and are now collectable items of retro clothing.