Q: How did “monster” come to mean something extraordinarily good (“a monster of the violin”) as well as something extraordinarily bad (“a bloodthirsty monster”)?
A: Let’s begin by going back to the Middle Ages, when the first lexical monsters stalked the English language.
English borrowed “monster” from the Anglo-Norman and Middle French word monstre, but it ultimately comes from mōnstrum, classical Latin for an omen, a monstrous creature, a wicked person, or an atrocity.
When “monster” showed up in Middle English in the late 1300s, it could mean something extraordinary, unnatural, or ominous, as well as a mythical creature like Cerberus, the many-headed dog that guards the gates of the Underworld.
Chaucer uses the term both of those ways in the two earliest written examples for “monster” in the Oxford English Dictionary.
In Boece (circa 1374), his translation of the Roman philosopher Boethius’s De Consolatione Philosophiae, Chaucer uses “monster” to mean something extraordinarily worrisome:
“I vnderstonde þe felefolde colour and deceites of þilke merveylous monstre, Fortune” (“I understand the manifold wiles and deceits of this marvelous monster, Fortune”).
In “The Monk’s Tale” from the Canterbury Tales (circa 1386), Chaucer uses the term for such mythical creatures as the half-man, half-horse centaurs, and the half-woman, half-bird harpies:
“Was neuere wight sith that this world bigan / That slow so manye monstres as dide he” (“Was never such a man since this world began / That slew so many monsters as did he”). The reference is to Hercules, who killed centaurs and harpies and kidnapped Cerberus.
Over the years, the noun “monster” took on many related senses, including a sea monster or other huge creature (c. 1450); a cruel, wicked, or otherwise repulsive person (before 1505); and an ugly or deformed person or thing (1715).
However, the word lost much of its negative sense when used adjectivally in the 19th century to mean extraordinarily large. Early OED examples include “monster ballroom” (1837), “monster product” (1839), “Monster Meetings” (1843), and “monster organ” (1845).
We assume that this gigantic sense of the adjective inspired the use of “monster” in the 20th century as both a noun and an adjective for hugely successful people or things, and for people with a great amount of knowledge or talent.
In the early 20th century, writers began using “monster” colloquially to mean remarkably successful, profitable, or good. The first Oxford citation is from the Sept. 22, 1912, issue of the Sunday Times-Tribune (Waterloo, IA):
“New Plays, new specialties and new people will add to the big show’s drawing power and the prospects for a monster week are bright.” (The word “monster” here is a noun being used attributively—that is, as an adjective.)
In the mid-20th century, according to the Random House Historical Dictionary of American Slang, writers began using the noun positively to mean “a formidable aircraft or automobile.”
The first two examples in the slang dictionary are from Aviation Cadet (1955), a young-adult novel by Joseph Archibald: “We’re really throwing the iron monsters around now” … “We thought cockpit procedure on the monsters was confusing.”
In less than a decade, the noun took on the sense of a remarkable or successful person or thing. The earliest Random House example is from an April 6, 1968, interview in Rolling Stone:
“Of course, man, she’s a monster. She’s like the best of that type of singer.” In the interview, the guitarist Mike Bloomfield is describing Aretha Franklin.
In that same interview, Bloomfield uses “monster” adjectivally: “When I was around fifteen I was a monster rock guitar player.”
And in the mid-1980s, according to Random House, it came to mean “a person having formidable knowledge or skill,” as in this 1986 example from the ABC television sitcom Head of the Class: “Darlene—a speech and debate monster.”
Today, the word “monster” can refer to all of the above: a mythical creature, a threatening force, something unusually large, someone extraordinarily wicked, a great success, a remarkable talent, and so on. It all depends on how it’s used.