Q: I assume “horror” gave us “horrible” and “horrific.” How then did “terror” give us “terrible” and (with a positive twist) “terrific”? Is “terrific” not rooted in “terror”? Or am I comparing apples and oranges?

A: No, you’re not comparing apples and oranges, but the etymology here isn’t quite as simple as you think. English borrowed these six words at different times from various versions of French.

Ultimately, all these words can be traced to Indo-European roots describing the way our bodies respond to fear.

The words “horror,” “horrible,” and “horrific” have their roots in the Indo-European base ghers- / ghrs- (to become stiff), according to the Chambers Dictionary of Etymology.

(We discussed these “horrendous” words in a brief posting back in 2007.)

The terms “terror,” “terrible,” and “terrific,” Chambers tells us, are rooted in the Indo-European base ters- / tres- (to shake).

Those Indo-European roots gave Latin the verbs horrere (to bristle with fear) and terrere (to fill with fear), which inspired the Old French, Middle French, Anglo-Norman, and Modern French words that gave English such frightening language.

The meanings of all six words reflected their scary or hair-raising roots when they entered English from the 1300s to the 1600s, according to written examples in the Oxford English Dictionary.

“Horrific” hasn’t changed over the centuries. It was first recorded in English in 1653, the OED says, and still has its original meaning: “causing horror, horrifying.”

But “terrific” is a different story. This adjective originally meant “causing terror, terrifying; terrible, frightful; stirring, awe-inspiring; sublime.”

The dictionary’s earliest citation for “terrific” in this sense is from Milton’s Paradise Lost (1667), which describes the Serpent in Paradise as a subtle beast “with brazen Eyes And hairie Main terrific.”

In less than a century, Oxford says, “terrific” took on a weakened sense: “Of great size or intensity; excessive; very severe.”

The earliest example of this new usage in the dictionary is from a 1743 translation of Horace’s lyric poetry: “How cou’d … Porphyrion of terrific size … stand against the Warrior-goddess?”

It took another century, according to the OED citations, for “terrific” to take on the modern sense of “an enthusiastic term of commendation: amazing, impressive; excellent, exceedingly good, splendid.”

The first example of this sense is from an advertisement in the Oct. 21, 1871, issue of The Athenaeum, a journal of science and the arts:

“The last lines of the first ballad are simply terrific,—something entirely different to what any English author would dream of, much less put on paper.”

Why did “terrific” evolve from “terrifying” to “excessive” to “amazing” in a little over two centuries?

We can’t say for certain, but English is a work in progress, as we pointed out in 2012. Words take on new meanings or revive old ones; new words are born and old ones die; a slang word becomes standard; a standard word takes on a slang meaning.

The evolution of “terrific” is an example of “amelioration,” a term for when a word’s meaning is elevated. The word “pretty,” for instance, meant cunning or crafty in Old English, and didn’t come to mean attractive until the 1400s.

The term “pejoration” refers to the opposite process, when a word’s meaning is degraded. The word “crafty,” for example, meant skillful or clever in Old English, and didn’t come to mean cunning in an underhanded way until the late 1300s.

[Update. A reader sent this comment about “terrific” on Jan. 15, 2014: “Oftentimes older Irishmen would use this word only in describing a tragedy such as a ‘terrific storm.’ My Polish uncle used to relate a humorous anecdote of trying to compliment his Irish immigrant future mother-in-law by telling her ‘the meal was terrific.’ As you might imagine, confusion, hurt feelings, explanations, and apologies ensued.”]

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