Search us!

Search The Word Detective and our family of websites:

This is the easiest way to find a column on a particular word or phrase.

To search for a specific phrase, put it between quotation marks.






Comments are OPEN.

We deeply appreciate the erudition and energy of our commenters. Your comments frequently make an invaluable contribution to the story of words and phrases in everyday usage over many years.

Please note that comments are moderated, and will sometimes take a few days to appear.



shameless pleading





Capricious / Mercurial

Get a grip, Muldoon.

Dear Word Detective: I’ve been trying to find any differences in the connotations of “capricious” and “mercurial.” They both deal with inconsistencies, but the only difference seems to be in their etymology: “capricious” started with the inconsistencies of goats, whereas “mercurial” started with the inconsistencies of the god Mercury. Is there anything more to these two words’ meanings? — Danielle Then.

That’s an interesting question. Say, do you mind if I borrow “The Inconsistencies of Goats” for the title of my next book? Usually I’d think of one myself, but all these goats are driving me crazy. I’ve tried to convince them they’d be happier outside, but they get halfway out the door and change their minds. Aside from a touch of agoraphobia, however, goats are just about the coolest animals going, much cooler than sheep, who are, let’s be blunt, total idiots. Goats are actually a lot like cats. Except for the horns, of course. I’m glad cats don’t have horns, aren’t you? Oh yeah, you had a question.

“Capricious,” which today we use to mean “impulsive,” “unpredictable” and, therefore, “unreliable,” is, appropriately, a word with a somewhat convoluted history. The noun behind the adjective “capricious” is “caprice,” meaning “whim, impulse, sudden urge or unusual action.” English borrowed our “caprice” in the 17th century from the French, who had adapted the Italian “capriccio,” also meaning “whim,” etc. But the earlier and original meaning of the Italian word was not “whim,” but “sudden shock” or “horror.” And the animal behind the word was not a goat, but a hedgehog. The Italian word is thought to be a blend of “caput” (head) with “riggio” (hedgehog), describing a person whose hair was standing on end, like a hedgehog’s, from fright or surprise. When “capriccio” eventually lightened up in Italian and came to mean “playful, whimsical,” the fact that it resembled the Italian word “capro” (goat) led people to associate the frisky play of young goats with “capriciousness,” which made much more sense than trying to rationalize “friskiness” with the torpid behavior of hedgehogs.

“Mercurial,” meaning “lively, volatile, given to quick changes of mood,” does indeed hark back to the Roman god Mercury (who was based on the Greek god Hermes), messenger of the gods and a notably fleet fellow (due in part to his winged shoes). Interestingly, Mercury was also the god of trade and travel, and his name comes from the Latin “merx,” meaning (and the root of) “merchandise.” “Mercury” today is best known as the name of a planet, an element, and a brand of car made, until 2011, by Ford. The adjective “mercurial,” which first appeared in English in the 14th century, can refer to anything having anything do do with Mercury, from the planet to the element, various plants, and medicines containing the element. The use of “mercurial” to mean “highly changeable” in reference to people dates to the mid-17th century and was apparently originally a reference to the fickle personality of the god Mercury. The modern use of “mercurial,” however, is more a reference to the metallic form of mercury (also known as “quicksilver”), which is the only metal which is liquid at room temperature. Apart from being extremely toxic, mercury is known for its highly fluid and quick movement, which is what makes it a good metaphor for swift change and unpredictability.

Every thesaurus I’ve checked considers “capricious” and “mercurial” to be synonyms, but I think there is a slight difference between the two. To describe someone as “mercurial” is not necessarily at all derogatory. Great artists and similar sensitive types are often lively, impulsive and given to “quicksilver” changes of mood. But to describe someone as “capricious” marks the person as undependable, flighty, and possibly petty, likely to disregard the effect of a sudden change in plans, etc., on other people. It’s not a distinction that can be traced to etymology or the broad definitions of the words, but I do think “mercurial” and “capricious” have developed that shade of difference in modern usage.

5 comments to Capricious / Mercurial

  • Kip

    In the same vein I have heard that the Isle of Capri was named for capric acid which comes from the goats that used to inhabit the island.

  • James

    A good well considered answer.

  • Gail

    Please update/comment in context of frequent use of “mercurial “ as applied to Trump. My take is that “mercurial “ has a positive connotation not applicable

  • Sandra Hennessey

    I read that the character Mercutio in Romeo and Juliet was so named due to his mercurial temperament. That idea predates your mention on its first use in English to the 17th Century. While Shakespeare didn’t use the word, you sense that it would have been an acceptable adjective to describe someone in his day. Of course, Shakespeare invented all kinds of words so maybe it wasn’t a common expression then!

  • Kevin Larmee

    Does no one else think that the word might come from the island of Capri, where the emperor Tiberius lived, and sometimes “capriciously” had his guests thrown to their deaths off the cliff?

Leave a Reply




You can use these HTML tags

<a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <s> <strike> <strong>

Please support
The Word Detective

by Subscribing.


Follow us on Twitter!




Makes a great gift! Click cover for more.

400+ pages of science questions answered and explained for kids -- and adults!