Q: When somebody tries to sell me a car and says, “Our prices are incredibly low,” he’s literally telling me that I shouldn’t believe him. Wouldn’t it make more sense to say, “Our prices are credibly low”?
A: The adjective “incredible” meant not credible when it entered English in the early 1400s, according to the Oxford English Dictionary.
And the adverb “incredibly” meant in an incredible manner—that is, not credibly—when it showed up around 1500.
The two words still have those clearly negative meanings today, but people began using them loosely—“in a weakened sense,” as the OED says—almost from the start.
In this sense, Oxford says, the adjective means, among other things, exceedingly great, and the adverb means exceedingly, extremely, and so on.
Those car dealers you mention are using “incredibly” to mean exceedingly or extremely or (we’d add) astonishingly.
The two words are derived from the Latin incredibilis (unbelievable), made up of the negative prefix -in and credibilis (worthy to be believed). The ultimate Latin source is the verb credere (to believe).
Here’s how The American Heritage Dictionary of the English Language (5th ed.) defines the two modern meanings of “incredible”:
“1. So implausible as to elicit disbelief; unbelievable: gave an incredible explanation of the cause of the accident.
“2. Astonishing, extraordinary, or extreme: dressed with incredible speed.”
The OED’s earliest citation for the adjective is from John Lydgate’s Hystorye, Sege, and Destruccyon of Troye (1412-1420).
In his Middle English poem, Lydgate describes as “incredible” (that is, not credible) an account of the Greeks put to flight during the Trojan War.
The dictionary’s first citation for the adjective used in its looser sense is from The Revelation of the Monk of Evesham (1482): “An inestymable and incredibulle swetenes of ioyfull conforte.”
The earliest OED citation for the adverb is from The Three Kings’ Sons (circa 1500), an English translation of a work by the French calligrapher David Aubert: “He had seen hem do in armes that day yncredibly.” The adverb here seems to be used in the looser sense.
An even clearer example of the adverb used loosely is from The Itinerary of John Leland, written sometime before 1552. In writing of his travels, the English poet and antiquary describes a church “adorned it with Gould and Sylver incredibly.”
We’ll end with the OED’s most recent example for the adverb used in its looser sense.
We’ve gone to the original to expand on this citation from English Traits, an 1856 book in which Ralph Waldo Emerson describes a meeting with Thomas Carlyle in Scotland:
“He took despairing or satirical views of literature at this moment; recounted the incredible sums paid in one year by the great booksellers for puffing. Hence it comes that no newspaper is trusted now, no books are bought, and the booksellers are on the eve of bankruptcy.”
Sounds familiar, doesn’t it?
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