decimate

Roget’s II: The New Thesaurus, Third Edition. 1995.
decimate
VERB: To kill savagely and indiscriminately: annihilate, butcher, massacre, slaughter.
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I'm not sure about complete turnaround. The 'savage and indiscriminate' sense is very definitely related to the archaic meaning of decimate. I don't get why linguistic evolution offends people. To me it's part of the magic of language that there is a continual shifting and rebalancing of what we mean.

If someone has ten apple trees and cuts one down, then says to me 'I have decimated my orchard', I can see why it's (etymologically) accurate and even funny in an ironic way. But in terms of current usage it's awkward and misleading. Personally I don't believe miscommunication is the point of language.

Hmm, the original meaning you give for dilapidate (taking apart of stones) is nonetheless close in spirit to the idea of decay and ruin, although it's true that the activity involved has shifted from deliberate action to mere neglect.

Whereas the shift in meaning for decimate represents a complete turnaround, from the killing of 10 per cent to the killing of "90 per cent". That's no doubt the reason why the shift bothers bilby's 5 per cent. (That would be pomegranate, me, and how many other people?)

In my case, as a good former linguistics student, I accept and respect the shift in common usage. But what happens in practice is that I don't feel I can use the word at all. It's not even like nice where one can, on occasion, make a nice distinction just for fun.

Actually pomegranate, linguistically speaking, common does tend to make it correct. A lot of words we use have different meanings now than when they were coined. We can't expect all words to keep the correct Latin meaning. delapidate, for example, doesn't mean what it does today, do you have a problem with that?

Not accurate in terms of origins, but correct in terms of current usage. I don't have many conversations with Roman legions. Well, have to differ on this one.

The 'kill in large numbers' meaning, for numbers over ten percent, is one of those cases in which dictionaries accept a second meaning because it becomes common usage. Common doesn't make it correct.

Too many? Would 95% be too many? "Too late!" she cried as she waved her wooden leg. You would be hard pressed to find a reputable dictionary that does not recognise the 'kill in large numbers' meaning.

Too many people use this word to mean "completely annihilate." In an American Civil War battle, if your side was only decimated, it probably won.