Those are the words you like to hear while looking for caves with your group. Yo yo means that you have found a cave and you are declaring your location for others to find you.
When a group of individuals are operating in a forest with a couple hundred feet between them, this simple technique conveys everything you need. First, it draws attention to the fact that you found a cave. Second it allows everyone to locate you if you are out of sight and to begin heading your way. Everyone knows they can abandon their search and can focus their efforts on hiking toward the shouts of “yo yo!”
“Yo yo” is actually a part of another term used by northwest cavers. Namely, the singular “Yo!” One “yo” announces your location, or can be used to ask for another’s location. For instance, if I’m a little turned around while hiking in the forest, I can shout “yo!” to my out-of-sight companions to ask for their location. In return, they shout “yo!” and from there you can determine if you need to change your direction or meet up with the other cavers.
Yo, and yo yo have been adopted by the Oregon High Desert Grotto, (the local caving club of central Oregon) many years ago. They borrowed it from the Willamette Valley and Oregon Grottos who are believed to have originated the terms. It is unknown as to the current spread of the terms, but they are still being used by all grottos of Oregon.