They hear words in conversation which they misinterpret and subsequently use incorrectly. Because they think they are smart.
E.g. the word sarcasm. It has become a floating, meaningless term. Or amp up.. yeah, like an amplifier. ‘Cept the phrase is ramp up.
Here comes Babel!
One of the millennials’ favorite words is “literally.” Some of them can’t speak two sentences without using it and it’s misused more often than not. Like you said, they think it makes them sound smart.