The following is taken from A History of the Hadiyya in Southern Ethiopia book by Ulrich Braukamper, 2012 pp 135/136. Thanks Assefa Lintiso for the reminder.
Rayyaa, Azaaboo and Ashaange are specified as the three sons of Hube’anaa in all of the traditions recorded. They were bom in Dallo where Hube’anaa is supposed to have lived. Rayyaa is just another version of Raayituu, the name of the clan still living in that area today. Hube or Hubaychoo dispatched his offsprings both to eastern Bale as well as to northern Ethiopia to Wallo and Tigray in 1530. The name Rayyaa designates the name of an ancestor and a descending ethnic group and it also stands for one of the four sections of the Arsi-Oromo which are defined according to topographical criteria, namely the area between the rivers Wabi Saballe, Ganaale and Wayb[Hadiyya concentration]. Present location of Rayyaa[Wollo and Tigray] is also deemed to be the original homeland of some Hadiyya tribes, like for example the Baadawwaachcho and Shaashoogo. This has already been mentioned in the analysis of the tribal legends with regard to the ethnogenesis of the groups concerned.
The name of Hube’anaa’s second son Azaaboo was preserved in an Oromo group in present-day Tigray’ though are Hadiyya geonologically and also the third son, Ashaange, is represented as an ethnic and geographic designation in the border area of Wallo and Tigray. According to Leemo -Hadiyya geonology Ashaange was a forebear who lived in Weera, not far from Lake Abbayya. Aashanchcho, derived from this name, has remained a common ethnonym of the Leemo until today and the traditional title of their rulers is asha ’n garaad.
What stands out more distinctly is that the Oromo pushed down from their locations in the highlands and assimilated with the Hadiyya in the lowland zones of Dallo and Lake Abbayya. They obviously absorbed them so completely in this region that since then the Rayyaa, for example, simply count as one of the “most senior” groups of all the Oromo. Of all the Hube’anaa descendants only a section of the Ashaange distinctively preserved their ethnic identity as Hadiyya, namely the Leemo-Gudaalla especially.
The advance of the Oromo into Hadiyya and Dallo presumably took place in the form of a peaceful infiltration in the course of which the old established people were not subjugated and sometimes even rose to leading positions. The Raayituu, the clan of the abbaa muuda, are genealogically related to the Haballo and identified as a group of Hadiyya descent, which is also confirmed by the Arabic names in the genealogies, However there is unquestionable evidence of their belonging to the historic Hadiyya already at the time of cAmda Sayon and Zar’a Yaleqob (cf. pp. xxx).
The Hadiyya and Oromo in the 16th century, were agropastoralists with similar economic strategies, their fusing together required no far-reaching cultural transitions and changes. With the extension of the gadaa system among the Hadiyya, the Oromo language asserted itself. This became a basic prerequisite enabling the Oromo to accomplish complete assimilation.