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.