The file
A word for a city slicker in 1883, a word for a surfer in 1965, and by 1982 a word for every human being, including your mother. Spicoli said it; Bill and Ted said it; Jeff Bridges built a religion on it.
It's the most flexible word Gen X gave the language: one syllable that can mean hello, no, I'm sorry, and look at that, based on the pitch.
Sources: Wiktionary — Dude · Wikipedia — Dude