Okay. If "slop" is a shortened form of "goyslop", then what's the etymology of "goyslop"? Is it just a wholly novel sequence of unrelated letters?

Goy is the Hebrew for a Gentile (or a nation). However, while goyslop is an earlier coinage I certainly do not link it to AI-slop, but more to "sloppy".

"Goyslop" and "sloppy" are both derived from "slop". "Goyslop" meaning "slop of the goy variety" (equivalently to "AI slop"), and "sloppy" meaning "having the qualities of slop".

I was already aware of the term "goyslop" but I see it as a parallel development rather than the origin. I heard daytime TV programming being referred to as slop over twenty years ago. I don't think there are any antisemitic undertones for the word outwith the "goyslop" coinage.