NONPLUSSED

Latin non plus — no more, no further. The original sense was of arriving at a point where there is nothing more to say: I am at a loss, I cannot proceed, my resources of response have been exhausted. The word named the bewildered, the speechless, the genuinely at sea.

At some point in American informal usage, the prefix non- began to be read as negation rather than intensifier — as meaning “not plussed,” where “plussed” was back-formed to mean “bothered” or “fazed.” And so nonplussed began to mean its opposite: unperturbed, cool, unmoved by whatever just happened.

This is the most recently formed contranym in the Codex — not a drift across centuries but a split within living memory. Two cohorts of educated speakers now use the same word to mean opposite things, each confident the other is wrong, and each correct within their own register.

The traditional reader sees “she was nonplussed by the announcement” and understands: she was at a loss, confused, taken aback. The American informal reader sees the same sentence and understands: she was unmoved, cool, entirely unfazed. The same sentence has two opposite meanings depending solely on which side of the split you were educated on.

Other contranyms in this Codex drifted across centuries, driven by institutional language, labor divisions, or phonological accident. NONPLUSSED did it in a generation, driven by misreading. It is the Codex’s most recent contranym and arguably its purest case of language making itself up as it goes.