Q: I was taught that the meaning of an idiom cannot be derived from the meaning of its words. For instance, “kick the bucket,” which refers to dying, not to kicking or buckets. But many expressions are called idioms even though they make some literal sense (“to keep an eye on,” for example). Doesn’t an idiom have to be nonliteral?
A: Your definition of “idiom” is a bit narrow. An idiomatic expression isn’t always nonliteral.
Broadly speaking, an idiom is simply a peculiarity of language. It’s an expression or some characteristic of speech that’s peculiar to a language, a region, a dialect, or a group of people.
For example an idiom can be, as you say, an expression that can’t be interpreted literally (as in “it’s raining cats and dogs,” or “he reached for the stars”).
But it could also be a speech form that’s grammatically unusual or that just doesn’t parse (“I could care less,” “that dress isn’t you”).
An idiom could be a specialized language or vocabulary used among a particular group of people—like doctors or journalists. Or it could be a particular regional or dialectal speech pattern.
And “idiom” is sometimes used in reference to artistic forms of expression (as in “the idiom of Greek Revival architecture” or “the idiom of Abstract Expressionism”).
The word “idiom” came into English in the 16th century from the French idiome, but its ultimate source is the Greek idioma, meaning a peculiarity or a peculiar phraseology. The root of the word is the Greek idios (one’s own).
In classical Latin, according to the Oxford English Dictionary, idioma meant a “special term or phrase used by an individual or group.”
In post-classical Latin (from the 7th to 13th centuries), idioma came to mean a language, a peculiarity, a special property, a dialect, or a spoken form of language, the OED says.
When “idiom” first came into English, in 1573, it meant the individuality or character of a language.
But today when we use “idiom” in the linguistic sense, we generally mean (and here we’re quoting one OED definition) “a form of expression, grammatical construction, phrase, etc., used in a distinctive way in a particular language, dialect, or language variety.”
The dictionary’s first citation for the word used in this sense is from a sermon, delivered by John Donne sometime before 1631, that cites “amen” as an example of an idiom:
“There are certaine idioms, certaine formes of speech, certaine propositions, which the holy Ghost repeats severall times, upon several occasions in the Scriptures. … How often does our blessed Saviour repeat his Amen, Amen?” (We’ve expanded the citation.)
Donne was right. “Amen” (which we’re written about on our blog) is a pretty good example of a form of expression used in a distinct way.
The OED does include the more specific sense of “idiom” you’re asking about: “a group of words established by usage as having a meaning not deducible from the meanings of the individual words.”
In other words, the nonliteral truth!
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