Proving once again that Oxford is way cooler than Merriam-Webster, the reference genuises at the former outfit have penned a thorough examination of the word "bro." Bros and their backwards caps, of course, have become the punchline of many pop culture jokes and think pieces, but the word also represents an interesting look at race and language, the Oxford blog points out. 

What they found was that the term "bro" used to refer to African-American men, a derivation of "brother." They write: 

Bro’s meaning had begun to expand by the mid-20th century. It came to refer simply to a man (a synonym of ‘fellow’ or ‘guy’), or sometimes more specifically a black man. The rock critic Lester Bangs wrote in 1976, "if we the (presumably) white jass-buffs couldn’t get with it maybe it was only meant for the bros."

That usage of the word shifted in the ensuing decades, partly through the general appropriation of African-American culture. There were other reasons, too: One of the turning points they unearth is the cultural touchstone known as Encino Man:

By the 1970s, though, bro began to break new ground, untethered from brother. It came to mean not merely a guy, but a male friend. For instance, in the film script for the 1992 comedy Encino Man, the stage directions state: “Stoney and Hank have been bros since grammar school.” 

It's been over 20 years since Encino Man was released in theaters. Today, as NPR pointed out, bros are predominantly white. Oxford explains that "by being the sort of person who says 'bro,' a person becomes a bro. In the immortal utterance 'don’t tase me, bro' it is not the person doing the tasing who is the bro, but the person being tased."

And the word going through one more shift, with the rise of the"Bromanteau" — including the brogrammer, brohemian and brobituary. "The punning potential of bro is difficult to resist, even when the results are groan-worthy; any word with a strong -o- syllable is fair game. Someone should do a study—they could call it their magnum bropus," Oxford writes. It's unclear whether Brody Jenner has already called dibs on that project.