To decimate is (1) to destroy a large part of, or (2) to inflict great destruction on something. A few English speakers reserve the word for its obsolete Latin senses—(1) to take a tenth of, (2) to divide into tenths, and (3) to put to death one in every tenth of, especially as punishment for mutiny1—but decimate has not been widely used this way for centuries, and the insistence that these are the word’s only acceptable definitions is misbegotten pedantry at its worst.
Among the roots of decimate are the Latin decem (meaning ten) and decimus (tenth).2 The newer senses have nothing to do with tens, which gives rise to the objections over the word. Yet if we were to reserve the word for its tens-related senses, it would have little use outside writing about ancient Rome or 17th-century taxation, so it would surely drop out of the language. Its newer senses are giving it a life that it wouldn’t have otherwise. Besides, etymology only rarely holds sway over English usage, and the language is full of words that have drifted far from their etymological roots.
“Newer” in relation to the modern definitions of decimate is a relative term. The OED cites one instance of the word used in the newer way from 1663, along with several from the 19th century. And in historical Google Books searches covering the late 19th and early 20th centuries, decimate is only used in the newer sense (except in writing about ancient Rome and in discussions of the supposed misuse of the word). So while we can gripe about the modern use of decimate being etymologically questionable, the change to decimate’s meaning is long established and irreversible.
Here are a few examples from historical sources:
Then the microbe will intervene, as it does periodically ; it will decimatepopulations and will sow death. [Popular Science (1895)]
Rinderpest and lung sickness decimate his cattle, locusts more than decimatehis crops, his young trees and plants are eaten by white ants, even his poultry have a special complaint. [Journal of the Royal Society of Arts (1899)]
The very fact that the present wet, cold weather is unsuitable for campaigns is calculated to decimate the Turkish troops. [Evening News (1912)]
Draft boards may further decimate the number of mature boys available. [Gettysburg Times (1943)]
It is no use arguing whether a major nuclear war would merely decimate the participating nations but leave enough of their peoples alive to start a new round of progress. [Bulletin of the Atomic Scientists (1963)]
Someone let dogs run free in the foothills of west Junction City, decimating Crawford’s nationally recognized herd of show goats. [Eugene Register-Guard (1985)]
And here are a few recent examples:
The closure came over the objection of lawmakers who said it would decimate Bent County’s economy. [Denver Post]
But farmers are forced to use pesticides to protect their fields against pests, chiefly aphids, which would otherwise decimate up to £120 million of wheat per year. [Telegraph]
Robinson has subsequently revealed he was a big seller of shares into the company’s decimated market price. [Sydney Morning Herald]