"Kumu" is a Hawaiian name for a type of fish, which is more commonly known as a triggerfish in English.
It's possible that there is a local name for this fish in another language that starts with "g," but it wouldn't be a standard English name.
What is another name for a fish called kumu starting with g?
There isn't a common English name for the fish called "kumu" that starts with the letter "g".