In 1993, id Software came out with Doom and the frag, and if you'll notice, in most games now (i.e Quake, Quake2) you can still very easily get fragged.

I'm not sure why John Romero & Co. had us fragged, but I do know where it came from...

The History of the Frag:
In the Vietnam war, Americans hit by shrapnel of fragmentation grenades were "fragged".
Don't ask me how being hit in the face with a BFG10K makes you fragged.