spelunker noun a caver US,1942 Ultimately from Latin spelunca (a cave).
— John Ayto, TheOxfordDictionaryofSlang, p. 355, 1998
In the 1980s, spelunkers entered a deep dive in Romania that had been sealed off from the outside world for a long but unknown period. — Bill Bryson, AShortHistoryofNearlyEverything, p. 369, 2003