bon ton en · NOUN
Etymology
Borrowed from French bon ton (literally “good tone”).
Meanings
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(dated, uncountable) The height of fashion; fashionable society.
This part of the proposition is very popular, particularly with the higher and middle classes, because it is the fashion, and a mark of bon ton, to enclose one's letter in an envelope, even though, or perhaps because, it subjects it to double postage.
1839, The Quarterly Review, volume 64, page 555: