The word "spelunking" only recently entered English. the obsolete noun "spelunk', meaning "cave" or "grott," was used in English from the 14th throught the 16th centuries, but the first recorded use of "spelunking" dates only from the 1940's, which is also when "spelunker," meaning "one who explores caves," was first recorded, say editors at Merriam Webster Inc. Both words come from the Latin word "spelunca," meaning "cave." there is a little evidence for "spelunk" as a verb meaning "to explore a cave," which was formed by back-formation from "spelunking."
The scientific study or exploration of caves is known as "speleology," and a scientist who engages in such study is a "speleologist." These words, both of which were first recorded in the late 19th century, are derived from another Latin source, "speleum," which also means "cave." "Spelunking" and "spelunker" are terms for the hobby of cave exploration and for those who engage in the hobby.