Etymology
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spelunk (n.)
"a cave, cavern, a vault," c. 1300, from Old French spelonque (13c.) or directly from Latin spelunca "a cave, cavern, grotto," from Greek spelynx (accusative spelynga, genitive spelyngos) "a cave, cavern," from spelos "a cave." An adjective, speluncar "of a cave" is recorded from 1855.
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spelunker (n.)
"a cave bug; one who explores caves as a hobby," 1942, agent noun formed from obsolete spelunk "cave, cavern." The verb spelunk "explore caves" and the verbal noun spelunking are attested from 1946 and appear to be back-formations.
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