John McIntyre’s latest column demolishes a reader who insists that decimate must be limited to reduce by a tenth”:
There you have the etymological fallacy at its finest. Because CanSpeccy can cite a handful of examples of the limited use of the word, the loose or rhetorical sense of “to subject to severe loss,” for which the OED has examples dating back to 1663, must be ignorant and anyone who uses it should get fifty of the best.
The giveaway is CanSpeccy’s sneer at “misuse on the basis of common usage.” Common usage is what determines language, which is an arbitrary set of sounds or letters that means only what the users agree they mean. That is why in English we can use decimate in a way that Caesar did not,* why we can appropriate words from Scandinavian languages and alter their pronunciation to suit ourselves. Common usage is why we no longer speak Anglo-Saxon or Norman French.
But that asterisk after “Caesar did not” goes to an interesting question: “Not a Latinist myself. Are we sure, really sure, that no classical writer of Latin ever used decimare in a loose or rhetorical sense?” Jan Freeman wrote me to suggest that “this seems like a question for your erudite band of readers,” and I agree, so: anybody know?