A variation (different way of saying)of off the chain. This term can also be associated with "fo sheezie my neezie" hence the term off the heezie. I guess everyone just figured "Off the chain" and "Fo' sho my nigga" were getting pretty old so people decided they had to update it a little. ya know make it ryhme, sound a little better.
Mike: "Yo I hit up the cub last night, fine hoes all up in that bitch"
Mike's Friend: "Word son? We hittin that shit up again tonight"
Mike: "Fo sheezie my neezie, it's finna be off da heezie"