snorkel n.

1944, "airshaft for a submarine," from German Schnorchel, from German navy slang Schnorchel "nose, snout," which is related to schnarchen "to snore" (see snore (n.)).

So called from some resemblance to a nose or to its noise when activated. The Englished spelling attested by 1949. The meaning "curved tube used by a swimmer to breathe under water" is attested by 1951. Compare earlier, now obsolete, English imitative word snork "to snort" (1807); "a snort" (1814).