[kmill]

I've wondered whether the term directly evolved from this sort of joke list that was popular to pass around on the early internet: http://www.personal.psu.edu/sxt104/program1.html

[codezero]

I assume it evolved not long after guns existed, and likely grew in the military :)

[kmill]

"Shooting yourself in the foot," sure, but if you look up "footgun" it seems to only be programming slang. What I was suggesting with the above comment was that this sort of list might have popularized the metaphor of shooting yourself in the foot in programming, which was then was subjected to hacker-style word manipulation.

[codezero]

Ah fair, yep, that's probably right.