Original: The very name of each Dalai Lama from the Second Dalai Lama onwards had the word Gyatso (in it), which means "ocean" in Tibetan.
Simplified: Dalai Lama is the title of Tibetan Buddhism leader. "Dalai" is original from Mongolian which means "ocean" and "Lama" is original from Tibetan which means "the highest principle".