yo james! if i'm not wrong...moshing all originated from early hardcore punk that emerged in the 1980s. Specifically 1980-1984. So bands like Black Flag, Bad Brains, Minor Threat that sort of deal. Although, people who know their moshing terms, will probably tell you that, that it's very diffrent from what it is now (they call that form of moshing skanking now), it basically created an aggressive way to dance to music.
but you guys have lumped everything thats aggressive into a single monolithic term called moshing. there's skanking, circle pit, kung fu, anyhow push-push, wall of death, crowdsurfing, stage diving, the worm (looks kinda lame, not the one that scotty 2 hotty wrestler guy does tho) and pogo (also looks lame, blame the sex pistols) etc etc....
i remember watching a doc on mtv, tales from the moshpit or something. Anyway, i just bullshitted this whole thing, so dont believe all of it.