What does CAY stand for?

Casualty - Telegraphy (PCTE)

Cayacraft Fiberglass Products, Lafayette, LA - Manufacturer code for watercraft hull identification number (USCG)

Cayenne - French Guiana - Airport symbol (OAG)

Cayman Airways Ltd. - British - ICAO designator (FAAC)

Cayuga - Language code (ETLW)

Come-All-Ye - A publication (BRI)