Win easily, with little effort.

Many phrases have originated as jargon in the world of sport, including several from boxing. The memory of Muhammad Ali dancing round the ring with his hands at his side and going on the win the bout might encourage us to think that that is the origin of this one. Not quite, although it does come from sport - horse racing.

Jockeys need to keep a tight rein in order to encourage their horse to run. Anyone who is so far ahead that he can afford to slacken off and still win he can drop his hands and loosen the reins - hence winning 'hands down'. This is recorded from the mid 19th century. For example, 'Pips' Lyrics & Lays, 1867:

"There were good horses in those days, as he can well recall, But Barker upon Elepoo, hands down, shot by them all."

It began to be used in a figurative sense, to denote an easy win in other contexts, from the early 20th century.