Words take on new meanings all the time. One of them is terrific. No, I mean one of them is “terrific.” It comes from the Latin word “terrificus,” which means frightening. But of course nowadays if you say something is terrific, you mean it’s marvelous and not frightening at all. Something like, I don’t know, this very post, perhaps.
“Terrific” is a fairly recent addition to English; it didn’t arrive the 17th century. John Milton was the first to use it, in Paradise Lost. He meant it in the original Latin sense of frightening:
“The Serpent suttl’st Beast of all the field,
Of huge extent somtimes, with brazen Eyes
And hairie Main terrific, though to thee
Not noxious, but obedient at thy call.”
In that passage he’s talking about a “serpent with a hairy mane,” which he probably lifted from Virgil’s Aeneid, which describes two man-eating serpents that way (sort of). As an aside, Virgil’s serpents weren’t snakes; they were more like some sort of sea monsters.
“Terrific” began a slow shift in meaning right away, driven by its metaphoric use by other writers. In 1743 Matthew Tower described a mythical giant (Porphryion, if you must know) as “of terrific size.” What he’s doing there is using the original “frightening” as a way to amplify “size.” He could have just said the giant himself was terrific. Thomas Dutton did the same thing in 1798 when he wrote “I am struck with admiration at the terrific sublimity of his genius.” Here “terrific” is modifying “sublimity;” an even clearer application of the word as a metaphoric amplifier.
In the following century terrific continued its advance into metaphorical use by showing up in advertising. In 1871 an ad in Athenaeum magazine included this:
“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.”
Another aside: notice that in 1871 it was common to say “different to” rather than “different from“. Both of these are used today, “to” more in the UK, and “from” more in the US.
Returning to “terrific,” the word was already being used as a standalone based on its metaphoric use instead of its original meaning. That approach spread at, well, terrific speed. In 1930 Denis Mackail published The Young Livingstones and included this:
“‘Thanks awfully,’ said Rex. ‘That’ll be ripping.’
‘Fine!’ Said Derek Yardley. ‘Great! Terrific!’”
So there you have it. From frightening, deadly sea monsters to an enthusiastic exclamation in just just three hundred years. That’s terrific!