First, Second & Third Era
Remarkably little is known about the history of Erenen in the First, Second, and Third Eras. No records of Elven colonies during these ages exist. Two notable schools exist within those that study Erenian history from this time: the Elusivists and the Unremarkablists.
The Elusivists argue that the absence of records indicates that there must've been something to hide. Elusivist meetings tend to be loud shouting matches, with academics fighting over theories such as "Erenen was a prison colony", "Erenen was where the Elves sent their ugly children", "Erenen was a landfill" and "Erenen was the seat of the Gods".
Unremarkablists, meanwhile, pose that there are no records because there was nothing of note that occurred. Their meetings tend to be succinct and solemn, with a brief roundtable in which it is confirmed that no one did indeed find anything about the history of the land at that time.
Fourth Era
Proof of settlement during the Fourth Era is plentiful, meaning that Erenen was settled then, or had always been settled.
Fifth Era
Starting in the Fifth Era, the island was occupied by various tribes and small settlements. Consisting of several city-states, it was not until the War of Shield and Spear that the island was truly unified under Amadeus Sinask, in the Founding of Erenen.