Sucks- originally short for "sucks c0ck" now a tv friendly word meaning "bad."
Nookie - derived from the word "nook," originally a very dirty word for a woman's privates, as bad as c*nt, now a cute tv word for sex, usually between mom and dad.
F*ck - originally a farming word meaning "to sow seed," now one of the dirtiest words in our language.
The list goes on…
Added (1). I almost forgot f-ggot, which originally just meant "bundle," then meant cigarette, finally ended up being an offensive word for a gay man.
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Isn't it funny how bad words turn into good words, and vice versa?