Sorta. In the aughts, Cheese Pizza was a code for child porn among those who didn't want interested parties (e.g. the NSA ) picking up the conversation during their normal webcrawling. Of course, since then, they caught on.

These days, the term is CSAM (Child Sex Assault Material) when discussed by those who see it as a problem (e.g. law enforcement and people who discuss the science of content moderation). It comes up frequently, because every time some politician or billionaire decides they're going to start their own free speech social media platform ( With blackjack! And hookers! ) One of the phases they have to go through is trolls (and others) posting CSAM without it getting taken down right away.

A more complex issue is what counts as CSAM and what doesn't (examples of controversies include the Napalm Girl picture of Phan Thi Kim Phuc, The Little Mermaid sculpture in Copenhagen and porn featuring The Simpsons family), and there is no consistent standard that applies to all social media platforms, but as laws are defined, the county, state and nation in which the platform is being used. Denmark is obviously fine with the mermaid statue, but some places are not.