Irish Fishermen's afghans

I've got to ask, what is an Irish Fishermans Afghan? I'm getting some sort of fisherman's jumper, an Irish one possibly (is there a special kind?-- I thought they were just sort of a-national jumpers, or should that be universal?), but the Afghan part has me totally flummoxed, I'm trying to figure it out but my mind is full of flum. Please tell me. [question-e]