At a loss for words. Also used in a more general way to mean bewildered. From the Latin non plus, no more, no further. That's simple enough. The word has been in use since the late 1500s. What's really odd is that, starting about ten years ago, it acquired the meaning "unimpressed" or "unmoved." No one knows how this happened. Perhaps people thought that it meant that someone was "not plussed." But there is no word "plussed" in English. This strange, new trend leaves me bemused - perplexed, lost in thought. "Bemused" has been around for 300 years. What strange, new meaning will it suddenly acquire?
(Will be published in the November 2009 issue of Denver's Community News.)
I'm collecting all of these at: http://www.dvorkin.com/davidsdefs.html