French, literally "good" (adj.), from Latin bonus "good" (see bonus). It has crossed the Channel in phrases such as bon appétit, literally "good appetite" (1860); bon-ton "good style" (1744); bon mot (1735), etc. Compare boon, bonhomie.
soiree n.
"evening party," 1793, a French word in English, from French soirée, from soir "evening," Old French soir "evening, night" (10c.), from Latin sero (adv.) "late, at a late hour," from serum "late hour," neuter of serus "late," from PIE *se-ro-, suffixed form of root *se- (2) "long, late" (source also of Sanskrit sayam "in the evening," Lithuanian sietuva "deep place in a river," Old English sið "after," German seit "since," Gothic seiþus "late," Middle Irish sith, Middle Breton hir "long").
The French fem, suffix -ée, from Latin -ata, was joined to nouns in French to make nouns expressing the quantity contained in the original noun, and thus also relations of times (journée, matinée, année) or objects produced.