Chinquo was Bollo's gorilla friend. We find out his story in The Call of the Yeti
Vince, Howard, Naboo and Bollo enter their cabin to find a mounted gorilla head on the wall. They apologise to Bollo and he tells them that the gorilla (Chinquo) was his friend. He tells them of how Chinquo always wanted him to go to the edge of the forest, but they were told it was too dangerous. But Chinquo kept bugging him, so Bollo chopped off his head.
Another part of Chinquo's story is told when Vince, Naboo and Bollo are in their van and need someone to drive. Bollo says that he can't and tells them of how when he was younger, he and Chinquo used to go driving around and Chinquo kept telling him to go faster, so Bollo chopped off his feet so he could not push the accelerator.