the.com/nightclothes
The outfit you'd never be caught dead in, worn nightly.
means Loose garments worn for sleeping, like pajamas, nightgowns, or nightshirts.
from A plain English compound stitched together centuries ago: night plus clothes, because medieval people slept nude and the wealthy who didn't needed a word for it.
Class markerDedicated sleepwear was once a luxury of the rich.
NightcapOriginally a literal hat, not a final drink.
PajamasBorrowed from Persian for leg garment, via India.