Are you confused by amused and bemused?
If so you're not alone. Bemused is one of those words whose meaning is shifting. Nonplussed is another. So is decimated of which I have previously written (somewhere I think - can't find it now).
Ironically the original meaning of both bemused and nonplussed is "perplexed", "bewildered" or "confused". Both words have since taken on different meanings which sorely perplexes those of us who actually know what the words are supposed to mean. Bemused is now often used to mean "slightly amused" and nonplussed to mean "unfazed". Methinks that it's the people giving them the new meanings that are confused.
How can such new and different meanings arise? Too easily, I'm afraid. People hear words they don't know and - instead of looking them up - guess their meanings based on context and in many cases by the meaning of similar sounding words (e.g. bemused, amused). Then they start using their newly acquired word in conversation and their equally ignorant (in the literal sense of the word) friends pick up the intended meaning from context, and away it goes. Spreading like cancer.
Thanks to my wife Donna for finding this 2008 article by Ben Zimmer: in thevisualthesaurus.com
Bryan Garner in his book "Garner's Modern American Usage" defines these as "skunked terms" and describes two groups of their users. Group 1 maintains the traditional meaning while Group 2 adopts the modern usage.
Zimmer asks his readers which group they fall in - traditional or modern - or both. He then suggests that when clarity is important the best strategy is to avoid these terms altogether.
But as one of his readers points out in a comment, if Group 1 (who knows the original meaning) avoids using the skunked terms, then Group 2 wins by default, and the meaning will shift. Only if Group 1 sticks to their guns and (to mix a few metaphors) with constant vigilance maintains the right [meaning], can the word survive in it's original sense. At some point the battle is lost (as I fear it is for decimate) and there is no turning back.
I have a foot in both camps. On one hand (to mix anatomical metaphors) I understand that language changes, and that this is neither good or bad in itself; on the other hand it grates on the nerves to see it happen.
Unlike the Queen, "We are all bemused!"