What does red jacket mean by this great island?

Red Jacket is referring to "America" by stating "this great island."

Explanation:

Red Jacket or Chief Red Jacket, in his childhood was named "Otetiani" meaning "always ready" and "Sagoyewatha" in manhood, which means "he keeps them awake." Red Jacket was born in 1750. He got his name Red Jacket by a British Soldier who gave him a red coat.  

Red Jacket once made statement:  

"Brother ... listen to what we say. There was a time when our forefathers owned this great island..."

Red Jacket in this oration while stating "great island" is referring to America.

"Your forefathers crossed the great water and landed on this island."

idk

explanation:

i think it is called the president's cabinet.