A spelunker is a Latin sounding term for caver. According to Merriam Webster, the word came into adventure sport lingo because of the author and outdoorsman Clair Willard Perry.
The word seems to be used a great deal in literature:
“I have no special desire to go crawl around in caves, but I really like the word [spelunking] and want to use it in conversation. I do a lot of things just to use words I like.”
― Evan Mandery, First Contact-Or, It’s Later Than You Think
“I love vocab. It’s like spelunking in a cave you’ve been in your whole life and discovering a thousand new tunnels.”
― A.S. King, Please Ignore Vera Dietz