Spring is in the air, and if a classic euphemism is to be believed, this means birds and bees have begun their time-honored practice of non-stop coitus.

Or something like that.

The phrase "the birds and the bees" is hazy by design—it's used to tell children about the mechanics of human sex without actually mentioning sex or humans. It's prudish poetry that has somehow endured throughout the years, but its origins—like its definition—aren't entirely clear.

Kathleen Kelleher writes in the Los Angeles Times that the term is thought to have two possible origins. Samuel Taylor Coleridge is credited with referring to the two species in the context of love in his 1825 collection "Work Without Hope":

All nature seems at work . . . The bees are stirring--birds are on the wing . . . and I the while, the sole unbusy thing, not honey make, nor pair, nor build, nor sing.

Unfortunately for Coleridge, this fleeting passage had a lasting legacy, and his jealousy at local birds and bees for getting more action than him has been etched into eternity.

USC professor Ed Finegan found an earlier use of the phrase in the diary of John Evelyn, published in 1644 (but written a century prior):

That stupendous canopy of Corinthian brasse; it consists of 4 wreath'd columns--incircl'd with vines, on which hang little putti [cherubs], birds and bees.

Finegan theorizes that Romantic era poets were inspired by this passage's placement of "birds and bees" so close to Cherubs, which represent the sexuality of humans.

The earliest use of the term I found in the New York Times archives that could conceivably be in the modern context of sex is from a Civil War correspondence from Washington DC, published a little over a week after the start of the conflict, in 1861:

It is a warm, sunny day, this 20th day of April. The air is redolent of bursting buds, and the Capital Park is jubilant with the gushing songs of the birds and the humming of the honey-bees. The Northern air that has "aggressed" upon us for a week past has been driven back by the rebellious South wind, that comes, fresh from the fair faces it has carressed, and the waving tresses through which it has wantoned, to enchant the soul with its balmy breath, and entrance the mind with its dreamy sweetness.

The author certainly doesn't shy from wordplay ("aggressed," sick burn), which leads me to believe that euphemistic speaking is a possibility.

On the bright side, the convoluted origins of "the birds and the bees" may inspire you to skip the phrase altogether next time you're asked, "Where do babies come from?"—assuming you're asked before Google is.