Every now and then, a bit of slang comes along that draws a bright red line between young and old. In 2012, that slang term is YOLO.

If you are over 25, YOLO likely means nothing to you. If you are under 25, you may be so familiar with YOLO that you’re already completely sick of it.

A tip to the oldsters: YOLO is an acronym for “You Only Live Once.” It shot to fame earlier this year thanks to the rapper Drake, whose song “The Motto” has the hook, “You only live once, that’s the motto...YOLO, and we ’bout it every day, every day, every day.” After a video for the song was released in February, the buzzword spread quickly among the high school and college-age set by word of mouth, not just in person but through the turbocharged vehicle of social media.

How quickly? Consider the lists of slang compiled every semester by students of Connie Eble, a professor of English at the University of North Carolina, Chapel Hill. YOLO was entirely absent from the submissions by Eble’s fall 2011 classes. By the spring semester, YOLO had become the most frequently mentioned slang term among the students, just edging out “totes” for “totally” and “cray” (or “cray-cray”) for “crazy.”

What accounts for the meteoric rise of YOLO, and how has it gone virtually unnoticed by nonmillennials? Its appeal to the youthful is self-evident. YOLO as a shorthand mantra defines youth, on a certain level. What is teenagehood if not the adventurous, often foolhardy, desire to test the limits of acceptable behavior—because hey, why not? YOLO!

The carpe diem sentiment of “you only live once” has a long history predating its punchy acronymic clipping. Garson O’Toole, on his Quote Investigator blog, traces variations on the theme back to the 18th century, as in this line from Samuel Richardson’s novel “Clarissa”: “We live but once in this world; and when gone, are gone from it for ever.” The exact wording of “you only live once” begins cropping up in the late 19th century, and by 1937 it was popular enough to be used as the title of a Fritz Lang film noir. One wry elaboration, credited to the comedian Joe E. Lewis in 1952, is “You only live once, but if you work it right, once is enough.”