The etymological fallacy is the faulty argument that the "true" or "proper" definition of a word must be its oldest or original meaning. Because most words undergo some degree of semantic change, the one reliable guide to a word's meaning is present-day usage rather than history.
Merriam-Webster's Dictionary of English Usage (1994) illustrates this point nicely:
One thing to remember when you read or hear someone insisting that an English word must have a certain meaning because of its Latin or Greek roots is that these insisters apply their etymologies very selectively. You will find few of them who object to December being used for the twelfth month, when its Latin root means 'ten,' or to manure being used as a noun meaning 'dung' when it originally was a verb meaning 'to work (land) by hand.' So when you read, for example, that caption must refer to matter above a picture because it comes from Latin caput 'head,' keep manure in mind.As Howard Jackson points out in Lexicography: An Introduction (2002), "Etymology . . . merely provides some passing insight for the interested dictionary browser with the requisite background knowledge and interpretative skills."
Of course you don't have to be a misguided purist to take an interest in word histories. For example, a brief tour of the Oxford English Dictionary can help us understand why, etymologically, there's . . .
- No Good in Goodbye
Goodbye is a contraction of the blessing "God be with ye."
- No Male in Female
Female comes from the diminutive of the Latin word femina ("woman"). It made its way into English through French as femelle.
- No Noise in Noisome
The adjective noisome has more to do with the sense of smell than the sense of sound. It's derived from the Old French word for "annoy," and means "objectionable, unwholesome, foul-smelling."
- No Limp in Limpid
Limp (an unsteady walk) is a word that goes back to Middle English. It's unrelated to the adjective limpid (clear or calm), which comes from the Latin word limpidus.
Still, it's best not to take such passing insights too seriously: above all else, "keep manure in mind."
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