shine one's knuckles

[trolley]

This line is from a news article I was reading on Rabble.ca.

“It won’t work, you know. She’s tougher than you. When Canada’s scumbags come at her, she shines her knuckles.”

She does what? and why? It would seem that she is shining her knuckles in preparation for a fight. I am a big fan of martial arts and have watched hundreds of bouts, over the years. I have never once seen anyone use this technique. I wonder if the author is referring to that gesture used to express self-congratulations…the one where you blow on your fingernails and then buff them on your lapel with that “figjam” (Fuck, I’m Good. Just Ask Me) look on your face. I’m not sure why she’d do that when scum bags are attacking, though. I can’t find a whiff of “shine your knuckles” anywhere on Google. Has anyone heard of this odd expression or did the author just make it up?

[Erik_Kowal]

Perhaps it is an allusion to knuckledusters (more commonly known as brass knuckles in the USA)?

[trolley]

Good call, Erik. Polishing up her brass knuckles makes a little more sense.

[Wizard of Oz]

Trolley there is the old gesture when one is confronted by knaves of a pugilistic character to close your striking fist and rub it in the palm of your other hand. This might be interpreted as the person "shining/polishing their knuckles".

WoZ in Aus
Taking off the gloves