I'm pretty sure "slop" in the sense used in "AI slop" is a word in common usage for any kind of cheap, low-quality, unpalatable edible paste, like gruel or anything of that nature, especially when it has a homogeneous consistency. It can also appear in verb form such as "slop it onto a plate", that is to scoop up the slop with a ladle or some other utensil and messily splat in onto a dining plate. It very much is not Internet slang, and I'd say it's quite an appropriate term for what it describes in its new meaning.