I went through a period of looking up a lot of words, especially for their etymology. I loved Indo-European roots, and discoveries like the fact that the words "black" in English and "blanco" in Spanish go way back to the same Indo-European word for lightning or maybe blaze: brilliant white light that leaves things charred black.
I was less interested in usage, which brings up judgements about right and wrong and when change is good and when it is only inevitable.
Recently I was going over a manuscript for a colleague, and came across a passage in which the narrator is on a walking pilgrimage and bares her feet to protect a developing blister with moleskin: "The other pilgrims were nonplussed," she writes. "One nodded sympathetically and one asked to borrow my scissors." These sentences completely nonplussed me. They didn't seem to match. If the other pilgrims were so shocked by her bare feet, why were they calmly asking to borrow the scissors?
Looking up words in the Internet age is far quicker than it used to be, although it has lost some of the comforting ritual that came with dragging down Eric Partridge's Origins or pulling out the magnifying glass for the compact OED. Within seconds, I had Googled "nonplussed," and the first definition was just what I expected, suggesting that my colleague was misusing the word: "surprised and confused so much that they are unsure how to react."
But wait! There was a second definition, labeled as a "North American" usage. Since my colleague is Canadian, I thought maybe that was going to be the explanation, a Canadian usage. The second definition was "not disconcerted, unperturbed"– pretty much the opposite of how I understood the word. I looked a little further and found a usage note saying that while in standard use "nonplussed" means "surprised and confused," a new use has developed in recent years, meaning "unperturbed." The new use may have arisen from an assumption that "non" is the normal negative prefix and must therefore have a negative meaning. The second "nonplussed" is not (yet) considered part of standard English.
Is this word is in the process of slipping over to its opposite meaning the way many people use "drone?" "Drone" seems well on its way from leaving its meaning of "non worker male bee" to something more like "drudge," possibly because of the boring sameness of the sound denoted by another version of "drone."
In the end, the writer decided to go with "unperturbed" just to make sure her narrative wasn't misread.