Is it ensure, insure, or assure?
1944, "airshaft for submarines," from German Schnorchel, from German navy slang Schnorchel "nose, snout," related to schnarchen "to snore" (see snore (n.)). So called from its resemblance to a nose and its noise when in use. The anglicized spelling first recorded 1949. The meaning "curved tube used by a swimmer to breathe under water" is first recorded 1951.