Gorilla (language)
From Tardis Wiki, the free Doctor Who reference
Gorilla was the language originally spoken by gorillas; such as one of the the Eighth Doctor's companions, Guy.
The Doctor understood gorilla, but he was never shown to speak it himself. The Doctor's understanding of gorilla caused him to promise to take Guy home to the Congo and it was used to communicate with Guy throughout their travels together. (AUDIO: AUDIO: The Mummy Speaks!)