I guess I was using the idiom wrong, it's apparently "take (one) down a peg" but I've always said "knock (one) down a peg," and when I say it I always pictured, in my head, a bunch of pegs lined up like stairs and someone being knocked "down" to a physically lower peg. it's actually one of the few idioms that prompts me have a mental image of it in my head.
I wonder what the actual origin of the idiom is.
"Violent" idioms are not uncommon:
"My wife is going to kill me when I get home."
"This company is raking me over the coals."
"That's it, the gloves are off."
"She's out for blood."
(Since I can't reply to the inner comment: - the phrase itself seems to have no solid canonical first reference but a few sources online say it's to do with ships and the navy, eg http://jimcofer.com/personal/2011/04/13/what-the-navy-gave-e..., I guess pick your favourite and run with it! :)
>It has been suggested... or... Either of these might be correct... 'pegs' could relate to many things.... it isn't clear what they were... Lacking any real evidence, we can't be sure of the origin.