Robin Williams is well-known for making this motivational Latin phrase the motto for his English class in the 1989 flick "Dead Poets Society." But that was certainly not the start of its popularity. The phrase was penned by Quintus Horatius Flaccus, aka the lyric poet Horace, in the first century B.C.E. Horace wrote in his "Odes Book 1":
Dum loquimur, fugerit invida
Aetas: carpe diem, quam minimum credula postero
This means, "While we're talking, envious time is fleeing; pluck the day, put no trust in the future." When you read the entire sentence, the full meaning becomes clear. Make the most of today, because there's no guarantee you'll be around tomorrow. And even if you are, who knows what tomorrow will hold?
While this expression has been uttered for millennia, it first wormed its way into the English language in the early 19th century, when the poet Lord Byron used it (he was an admirer of Horace) [source: Martin]. Many English proverbs, incidentally, lecture us to be wise with our time, such as, "Strike while the iron is hot" and "The early bird catches the worm."