Question

What does red jacket mean by this great island?

Answer 1

Talking about the Americas in the late 1400's.
columbus made three voyages from Spain in 1493, 1498, and 1502. ( the British main coats for officers, and/or other military ranks wore red coats aka jackets.) he explored the Caribbean island of Hispaniola. 
he was talking about the British in the late 1600s

I hope this helps in some way!

Answer 2

Answer:

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."