party clothes; evening wear; formal social attire
Refers to clothing suitable for formal social occasions such as parties, receptions, or evening events. Not everyday wear.
I plan to wear party clothes to the party.
That shop carries men's evening wear.
Compound of 社交 (しゃこう, 'social') and 服 (ふく, 'clothing'). The term is straightforward and modern, with no obscure historical derivation.