1) "Y'oh-kay!"
meaning okay, originating from O.K., which originated as a military term for "on kill" meaning the target is well... targeted correctly and everything's okay.
These slang words, when fully sounded out, mean "F-U-C-K Y-O-U"
Some people write, draw, or text this sentence to someone just because they are scared of fully just saying "fuck you."
And most adults, supervisors, or teachers wont notice it. They would this its just some funny slang for no reason or another.