Every once in a while the word “spelunking” shows up. It means “exploring caves,” which is something done by a “spelunker.” It seems pretty strange; there’s really nothing about crawling around inside caves that would suggest a word like “spelunking.”
The modern English word “spelunker” is relatively new; it appeared in the 1940s, and seems to have originated in New England. As with “spelunker,” “spelunk” did come into (rare) use, but no longer as a word for a cave. Now it’s a verb, meaning to explore a cave. But where did it come from?
There are two aspects to the answer. One is that “spelunk” once meant “cave” in English. It was from the Latin word “spelaeum,” and is related to the Dutch word “spelonk” and the German word “spelunke” — the German version is still in use, but nowadays means a low-class bar. However, we can’t really credit the original English version of “spelunk” as the predecessor of “spelunker” or “spelunking” because the last time it was mentioned in print was in 1563. “Spelunk” entered the language, but after that seemed to crawl into a cave and completely disappear for a few centuries.
The second part of the answer is that in the 1890s there was apparently a resurgence of interest in caves, and in France the “Société de Spéléologie” was formed. Around the same time the French versions of “speleology” (study of caves) and “speleologist” appeared. “Speleology” was not, at first, a formal scientific discipline. It was a hobby, and the society itself was founded by a lawyer, Eduard Martel.
“Spelunk” as a word for a cave didn’t re-enter English, but in the early 1940s “spelunker” did. It might have come from the French words, but it might also have been coined based on a completely different Latin word, “spelunca,” which in turn is based on the Greek word “spelynx.” All of those terms have to do with caverns, caves, grottos, and the like, and the root word of the whole works is the Greek “spelaion,” which is another name for a cave.
Speleology is now a legitimate scientific field, but speleologists don’t call themselves “spelunkers.” They seem to be a pretty practical group, and just call themselves “cavers.” In the caving business, “spelunkers” just refers to hobbyists and amateurs.
