> By the early 17th century nonplus was being used as a verb, with the meaning of “to cause to be at a loss as to what to say, think, or do.” Then, as now, the

> By the early 17th century nonplus was being used as a verb, with the meaning of “to cause to be at a loss as to what to say, think, or do.” Then, as now, the word is often encountered in its participial form (nonplussed), with a meaning that is nearly synonymous with “perplexed.” I never knew this meaning - as far as I remember I've always interpreted it as some form of "unconcerned" / "that's not relevant to me". I guess by outward appearance "at a loss for words" and "unconcerned" are kinda similar, even if the cause is different, which is why it's always fit well-enough in context.