This is an Old English term used by Tolkien to mean an unlikable, rude person. Oddly enough, such people still exist today. We call them assholes. However, if you wanna clean up your language or you're somewhere where the word "asshole" as a human descriptor works but would be unwelcome, then "churl" is your word. It's a great way to call someone an asshole
without calling them... An asshole
and we all know plenty of those.
My new boss is a complete churl.
Or: You don't have to be such a churl about it.
Or: Good luck, churlgirl.