Common noun; historic British usage (“Lyons tea-shop waitress”) and extended sense “one that nips”.
Definitionen
(historical, Britain) A waitress employed in J. Lyons & Co. tea shops, noted for smart uniform and brisk service. In 1920s London, a nippy could serve an entire dining room in record time.
An animal or person that nips or bites. Watch out for that pony—it's a real nippy.