Four years ago, when then-President George W. Bush surveyed the losses suffered by congressional Republicans in the midterm elections, he memorably called it a "thumping." On Wednesday, President Obama used a similarly colorful term to describe his party's electoral woes. "I'm not recommending for every future President that they take a shellacking like I did last night," he said at his press conference. That comment led many to wonder, how did shellacking come to describe a thorough defeat?

Shellac is a kind of resin made from the secretions of a tropical insect known as the lac. It has had many practical applications over the years, from the varnish on hardwood floors to gramophone records. The word entered the English language around 1700, combining shell and lac. (It's a translation of the French phrase, laque en ├ęcailles, "lac formed into thin plates.") In the 19th century, shellac developed a verb sense meaning "to coat with shellac," as a wood finish.

In the 1920s, the verb shellac started being used for slangier purposes in American English. Its passive participle, shellacked, turned up in a widely syndicated 1922 newspaper article explaining "flapper" slang to baffled parents. In the April 7, 1922 Milwaukee Sentinel, the article appeared under the headline, "Fathers and Mothers Must Learn Flapper Talk to Know What the Younger Generation Are Saying":

Daughter: "...After that we drifted to a couple of the clubs, and both the boys got beautifully shellacked."
Mother: "Shellacked! I don't understand."
Daughter: "Jammed, both of them."

An accompanying glossary explained that these were new slang terms for drunkenness: "Jammed: Intoxicated, bolognied, pie-eyed, piffled, shot, shellacked, canned, out like a light, stewed to the hat, potted, jiggered, tanked." (And if you want a few thousand more synonyms, check out Paul Dickson's book, Drunk: The Definitive Drinker's Dictionary.)

Why would flappers equate intoxication with being covered in varnish? That was beyond the understanding of "Mother" in the colloquy, but we can take some educated guesses. Evan Morris at The Word Detective conjectures:

I would guess that it comes from the fact that shellacking is often the last step in furniture manufacture, so when someone is "shellacked," he or she is absolutely, positively finished and done. The "very drunk" sense of "shellac" may also be a reference to liquor so strong (or cheap) that it tastes like shellac.

My own theory is that the youth of the 1920s hit upon the word as a way to convey an extremely stuporous condition, as if one were sealed up with shellac. Its obvious model is plastered, which the OED dates to 1915 as a term for drunkenness. Perhaps shellacked suggested an even further descent into inebriation, since a shellac varnish could be seen as more substantial than plaster. ("I wasn't just plastered, I was shellacked!")

A couple of years after the flapper story, the verb shellac surfaced in a very different context: boxing. In pugilistic reporting, it could be used as a transitive verb, meaning "to pummel thoroughly." The earliest example I've found is from 1924:

The smart Mr. Shevlin was biding his time, however, and when the opportunity came in the third he took full advantage of it and shellacked Norton plenty, ripping both hands to the mid-section with much power behind each drive.
Evening Tribune (Providence, R.I.), June 3, 1924

More frequently, it was used as verbal noun, shellacking, to describe a harsh beating:

At the end of the third round the Tiger was giving his man a thorough shellacking against the ropes.
—Indiana (Penn.) Evening Gazette, Feb. 27, 1925

As long as I live I shall never forget the beating I received at the hands of Joe Rivers... What a shellacking I got.
—Los Angeles Times, Mar. 1, 1925 ("My Hardest Fight" by Johnny Dundee, originally in Ring Magazine)

What was the connection between the drunken flappers and the pummeled boxers? In both cases, they might feel dazed to the point of immobility, like they were dipped in shellac. A boxer who has been metaphorically shellacked would quickly hit the canvas.

Very soon, the shellacking of the boxing world was extended to other sports, like baseball. Here, an unsuccessful pitcher is the one suffering the beatdown:

The Tigers brought their percentage up to the .500 mark by taking a double fall out of the Indians, 4 to 1, and 7 to 4. Dauss pitched laudable ball in the first game and Karr got a shellacking in the second.
—Atlantic (Iowa) News-Telegraph, June 30, 1925

So the groundwork for Obama's shellacking was already laid by sportswriters 85 years ago. As the term caught on, whatever connection it might have had to the substance shellac faded away, so that now the original metaphorical leap is hard to reconstruct. Some sources suggest the slang term first gained traction in the criminal underworld and prisons, which would make its origins even murkier.

Regardless of that early history, I believe shellac was ultimately successful in the "beating" sense for reasons having to do with the sound of the word. The first syllable, shell, is also a verb meaning "to bombard" (from the noun shell referring to an explosive projectile). And the second syllable, -ac, is reminiscent of such words as whack, smack, and attack. Thanks to all of these similar-sounding words, it is easy to understand a shellacking as a drubbing or trouncing, without worrying too much about what it once had to do with varnished floors.

Update: On the American Dialect Society mailing list, Garson O'Toole reports an even earlier baseball usage, predating my boxing examples. A headline for the Hartford Courant of June 25, 1923 reads, "Luque's Streak Ends When Cubs Shellac Reds, 2 to 0."