put up one's dukes
Possibly by analogy to a king or other ruler summoning his dukes, and by extension the duke's knights or other soldiers, to battle an enemy. Another possibility is Cockney rhyming slang as explained at duke.
- (idiomatic) To raise one's clenched fists in front of one's body and stand in a threatening or defiant manner, in preparation for a fistfight.
1886, Edward Money, The Truth about America, page 206:
- The proceedings of the State Democratic Convention, held at Turner Hall, yesterday, were disgraceful enough to bring a blush even to the cheek of a Democrat. "Liar," "snide," "put up your dukes, if you want to fight," catcalls, hooting, and yelling filled up a greater part of the deliberations of the august body.
- (idiomatic, by extension) To take firm action or to show oneself to be committed to such action, as when competing in a sporting event or other contest.