...I really wish Normies scum wouldn't try to pretend that they understand where internet language came from. I'll explain, it came up like pretty much everything from dealing with the #GG controversy. If you know anything about it, it was pretty much started from multiple media sources coordinating and releasing what amounted to the same information (pre-thunderclap) and this had a pretty radical left spin to alot of the times.
Amongst other stuff was a ton of articles about open marriage, but always in the form of only the wife being open. There were alot of other nontraditional sexual practices explored but they weren't really defended by most of the left. This was then compounded during the American Republican primaries where prominent CPac's were trying to get rid of this term and tweeted that they were proud to be Cucks if cucks meant racist whatever... this really got solidified as the term though when Trump won and Pornhub released their list of most viewed tag by state, and California's was "cuckold."