Not sure where it originated, but I first heard it to refer to a group of D&D players who, for all intents and purposes, live in the woods and emerge to kill things and loot their corpses, maybe the people being slaughtered are evil, maybe they just got a little annoying while haggling, maybe they just had a really cool coat someone wanted. Who knows!
This is why wizards frequently buy a house or tower or something to have a base of operations, and no one can call me a hobo. Hell I provide free housing for the hobos that manage to not get fireballed into "quitting the group for a quiet retirement." That's not a euphemism, my wizards made sure to have resurrection spells at least on standby.