(The Dude t-shirt, now on sale at the NeatoShop)
So, like, what, dude, is a “dude”? In The Atlantic, J.J. Gould traces the origin of the word. In modern English, the context matters a lot:
Dude may be the most Mandarin Chinese word in American English. In Mandarin, depending on how I intone the single syllable ma, I could be saying “mother” (mā), or I could be saying something as radically distinct as “horse” (mă).
Dude has a comparable quality. Just think of the last time you did something awesome in the presence of a friend who affirmed your awesomeness with the exclamation Duuude! Or the last time you said something objectionable to someone who began setting you straight with a firm and sober Dude. There may not be any obvious difference in denotation between these cases, but the difference in connotation is, you’ll appreciate from experience, pretty major.
Dictionary definitions, Gould goes on to say, seem to have little to do with popular usage but rather fit older times. A dude may be defined as a dandy, which it did in Nineteenth Century America. But more recently, for a man to call another a dude is to affirm a common bond of masculinity. It’s an expression of familiarity from man to man. Though, Gould notes, women often use it, too.
-via Glenn Reynolds