Clan Utaiharo
Spoilers ahead, proceed with caution
Piecing together what we can from the available sources, it seems that the clan Otiolo was a young, fairly minor tribe. Marlowe’s text says the Prince Aranata took its people “out of Utaiharo.” This suggests that Prince Aranata defeated another prince in combat and took his tribe for his own, making him the first chieftain of the Itani Otiolo, as any Cielcin who kills an Aeta becomes an Aeta. Such short-lived clans appear to have been common among the Cielcin, their being a species of tyrants (which explains the necessity of the Baetan class, who appear to maintain the continuity of the tribe as it changes hands and identities as it moves from Aeta to Aeta.
Tor Paulos, Howling Dark
Mentioned in Howling Dark, Chapters 56, 57, and 60.