Comment by wlonkly

But "slop" has meant low-quality stuff for a very long time. See also "swill", both analogies to pig feed.

The earliest OED2 citation of "slop" for the sense "figurative. Nonsense, rubbish; insolence" is 1952. Slop was slop long before "AI slop" was coined, and AI slop is slop from an AI.