Cuck is a word used by alt-righters to describe anybody weak, specifically a conservative who compromises some of their values to the "liberal agenda". This term, popularized on deeply conservative message boards in election-season 2016, derives from the much older word cuckold, the "husband of an adulteress" and a type of person typically stereotyped as weak, because they couldn't keep a partner. Cuckold has quite the diverse history. In Middle English, it was spelled either as kukewald or cokewold. Both of these alterations come from Old French cucuault, which is a formation off of cocu, the word for "cuckoo" (because the female cuckoo is known for changing mates) and the Germanic suffix -ault, which had pejorative connotations. Cocu is onomatopoeic in origin, as it's meant to be imitative of the actual cry of a cuckoo. -Ault comes from Frankish walda, meaning "authority".
Adam Aleksic, a freshman studying linguistics at Harvard University, has been described as the internet's sixth most famous etymologist. He has disturbing interests in words, vexillology, geography, board games, limericks, and law, and he loves writing about himself in the third person.
The Etymology Nerd