Enallage: Substitution of one grammatical form for another that violates a grammatical rule. Pronounced almost exactly like analogy, but from a different Greek source, ἐναλλαγή, which means “change.” (Analogy can be traced back to ἀναλογία, which means mathematical proportion or correspondence.)
I learned enallage only recently, but it turns out I was very familiar with examples of it. Mark Forsyth (@InkyFool on Twitter) dropped the word into a recent New York Times column about the rhetoric behind successful slogans. Here’s the relevant passage:
The other day I told a friend I was writing an article on corporate slogans. He immediately told me that the one he hated, absolutely hated, was “Think different” because it should be “think differently.”
He’s right, grammatically. But the fact that he’s nursing a grudge over an ad slogan Apple hasn’t run for a dozen years proves just how memorable it was.
Same for a long-popular British slogan, “Beanz Meanz Heinz,” which grammar would have insisted on as “Beanz Mean Heinz.”
For that matter “Got milk?” is substandard speech. So is Subway’s “Eat fresh.” Probably the most memorable ad in Britain in the last few years uses the one-word tagline “Simples” — uttered by an anthroporphic Russian meerkat on behalf of an insurance website, comparethemarket.com.
It’s a trick called enallage: a slight deliberate grammatical mistake that makes a sentence stand out.
“We was robbed.” “Mistah Kurtz — he dead.” “Thunderbirds are go.” All of these stick in our minds because they’re just wrong — wrong enough to be right.
Forsyth—author of The Elements of Eloquence: How to Turn the Perfect English Phrase—also discusses alliteration (“Famously Fresh” – Planters); diacope (“a verbal sandwich of two words or phrases with something else tucked in the middle,” as in the U.S. Army’s long-running “Be all you can be”); chiasmus (“I am stuck on Band-Aid*, ’cause Band-Aid’s stuck on me”); and tricolon (“Buy It. Sell It. Love It.” – eBay); and paradox (“The world’s local bank” – HSBC).
For more on enallage in slogans, see my Visual Thesaurus column “‘Bad’ Grammar in Advertising: License to Annoy?” (no longer paywalled).
* Always singular, although usually remembered as “I’m stuck on Band-Aids.” For pedantic legal reasons, the jingle inserted “brand” after “Band-Aid,” which ruins the symmetry.