Originally, the word “dude” meant “an old rag”. A “dudesman” was a scarecrow, built out of scrap cloth. In the late 1800s people started using it to describe a overly-well-dressed dandy. But then in 1981, Sean Penn’s use of “dude” in Fast Times at Ridgemont High singlehandedly caused a renaissance in the use of the word, to the point where an enormous cross-section of America now uses it.

So what, today, does “dude” mean? To find out, University of Pittsburgh linguist Scott Keisling decided to mount an investigation. He listened to conversations with fraternity brothers that he’d taped back in 1993, and had his undergraduate class record the situations in which they heard “dude” used in a three-day period.

What’d he find? The reason “dude” is so big these days, Keisling says, is that it evokes “cool solidarity” — a sense that you’re familiar and close to the person you’re talking with, but not, uh, too close. As Keisling notes on his web site:

The term is used mainly in situations in which a speaker takes a stance of solidarity or camaraderie, but crucially in a nonchalant, not-too-enthusiastic manner. Dude indexes a stance of effortlessness (or laziness, depending on the perspective of the hearer), largely because of its origins in the “surfer” and “druggie” subcultures in which such stances are valued. The reason young men use this term is precisely that dude indexes this stance of cool solidarity. Such a stance is especially valuable for young men as they navigate cultural Discourses of young masculinity, which simultaneously demand masculine solidarity, strict heterosexuality, and non-conformity.

In other words, if you’re a guy, “dude” lets you appear casually relaxed around other men, while still ensuring everyone knows you’re not gay. Not that there’s anything wrong with that. As you might expect, men use “dude” much more than women, but some women do use it to refer to other women, and as Keisling notes in a paper he wrote on the subject, “Men report that they use dude with women with whom they are close friends, but not with women with whom they are intimate”.

If you want to see the paper yourself, it’s online as a PDF here — and, perhaps as befits the topic, is quite stylishly written, so it’s fun to read. But to really bake your noodle, download the Excel file Keisling compiled of his raw data: Records of all the instances in which his students heard “dude” used. That graphic above is a snapshot of one part of the file.

For ever more “dude” scholarship, check out the excellent debate on the Language Log blog discussing the polysemous uses of “dude” — when it is the sole word used in extended conversations, as in a Zit cartoon and a witty scene from BASEketball.

(Thanks to Plastic for this one!)