A Knick is short for knickerbocker. It's a style of pants originally worn by dutch settlers and thanks to a book by Washington Irving, eventually became a nickname for Manhattan natives, particularly those who could trace their lineage all the way back to Dutch settlers.

https://en.m.wikipedia.org/wiki/A_History_of_New_York

Canadians are often referred to as "Leafs" (I've definitely heard and probably said "Shut up, Leaf!" to a Canuck before... hey, Canucks are a sports team too!) and Knickerbockers were pretty much exclusively a white person fashion thing but that's admittedly a stretch.

* oh and of course Canadians have been white forever.

Still, point stands firmly that other races are bitches for taking words too seriously. And, in their defense (red niggers anyway), it mostly wasn't them complaining about being called "redskins" or "indians," it was dipshit sjw and jews being offended on their behalf.