Its always cool to know how people got their handles, to see where was their inspiration.
Mine was of 3 (yes yes, toj'ers only):
1] When I was learning WWII in History, I saw a cool thing, there was a Canadian Corporal that died from a machine-gun nest, it said, that Corporal was the last Canadian in WWII, which is very heroic.
2] Knickerbockers kinda knew it, I could not think of a good animal and since I'd always play StarFox/ StarFox 64, well, Fox seem reasonable.
3] I like the ranking system, but I didnt want to be too high or too low, Admiral and Commander was too high, I'm not a leader anyways, and Private was too low. I played Starcraft for a while, and saw the Firebat had Corporal as rank, it was higher than a Private and lower than a Commander, so Corporal looked reasonable.
In short, Corp_fox, Corpfox, *Corp.fox*, Cpl.Fox, Corporal.Fox, etc.