The Rer Bare (or Rerebere, Rer Shabelle) are a tribe in Ethiopia's eastern Ogaden region on the Shabele River, near Somalia, who currently speak Somali. They appear to have shifted to Somali from a now-extinct language.
Their unattested but apparently non-Somali language seems to have been first mentioned in print by Lionel Bender in 1975:
D. W. Mcclure, Sr. first reported to me the presence of Sudanese immigrants on the Wabi Shebelle River at Gode in the eastern Ogaden. They are said to have their own language, bearing the given name [Rerebere]. Later Taye Reya informed me that Sudanese immigrants are found along the Ganale and Dawa Rivers as well, and that they are referred to by the Somali as rer bare (rer means sub-tribe in Somali.) They are also known as adona, and they speak Somali as well as their own language... I cannot say with certainty whether they speak one or more languages of what any of them is... So far no linguistic data has come my way.
Others have linked the Rer Bare to the Bantu language family, implying that they may be the remnants of a Bantu-speaking pre-Somali population or, like the "Somali Bantu" in the Jubba River valley of southern Somalia, the descendants of Bantu slaves imported from other parts of East Africa in the 19th century. Tobias Hagmann refers to them as "Somalised Bantu". According to Ulrich Braukämper:
The Adonē, a dark-skinned Somali-speaking population on the banks of the Wabi Shäbälle, are obviously the offspring of Bantu slaves who settled and expanded there since the 19th century.
A British hunter, Colonel Swayne, who visited Imi in February 1893, relates that he was the guest of Gabba Oboho, a chief of the Adona, for several days.