Aravir
From Tolkien Gateway
The son of Aranuir, who led the Dúnedain of the North during the closing years of the Watchful Peace. It was Aravir, it seems, who devised the name 'Aragorn'; he gave it to his son, who succeeded him as Chieftain Aragorn I. The Aragorn of the The Lord of the Rings was his distant descendant, Aragorn II of the line of Isildur.