1. "Hipster". New slang, right? You associate it with twentysomethings with skinny jeans and beards.
That’s because of a thing in linguistics called the “recency illusion”.
This is the impression that words you've recently heard are brand-spanking-new to the language, when in fact they're surprisingly old. (The term itself is, ironically, relatively recent: it was coined in 2005 by a linguist called Arnold Zwicky.)
It means we tend to think some new slang has just dropped from some teenager's mouth a few minutes ago. Usually, though, what we think of as some gleaming modern coinage is years, decades, or sometimes centuries old.