Bokkongngo' along the cliffs in Hagåtña
BOKKONGNGO' = bomb shelter, air raid shelter. It comes from the Japanese word bokugo meaning the same thing.
It's no surprise that the word is Japanese because Guam had no bokkongngo' until the Japanese built them in preparation for the American invasion in 1944. Some Chamorros were also forced to dig the bokkongngo'. Not too long ago you could go into some of them and find World War II relics : bottles, shell casings, uniform buttons.
The Chamorro word for "cave" is liyang.