Other forms: nappies
A nappy is the absorbent wrap a baby wears. Change a nappy, a wet nappy, nappy rash.
This is the British word; American English says diaper, which is the older of the two and was carried across the Atlantic. Nappy rash is the ordinary irritation of skin kept damp. Nappy also describes tightly curled hair, a use with an ugly history in America.
1nounnappyThe absorbent wrap a baby wears.
“The baby started crying, so her dad went to change her nappy.”
nappy is a garment.
Also accepted in games: diaper
A shortening of napkin with the -y ending, recorded from the early twentieth century. Napkin is itself a diminutive.
A diminutive in -y. The base is probably napkin but possibly French nappe directly (note that napkin is already a diminutive).
Etymology from Wiktionary, CC BY-SA