The story
From diaper + wrap. First sense probably from the Diaper Wrap patented product filled by American inventor Marion Donovan on 19 January 1949 (see quotations).
Etymology from Wiktionary, CC BY-SA 4.0.
diaper wrap
Today it means: Synonym of plastic pants (“an undergarment worn over a diaper/nappy (or underwear) in order to prevent leakage through the fabric.”). Full definition →