Put up your dukes!

Put up your dukes!

A challenge to fight. The “dukes” in question were fists, which the challenged party was asked to clench in preparation to trying to punch his opponent. But why “dukes?” The word comes from Cockney rhyming slang “Duke of York,” meaning “fork,” held at mealtimes by a clenched fist. Similarly, “duke it out” remains a general term for fighting.
See also: put, up