The origin is uncertain. Often compared to Proto-Indo-European *h₃órbʰos (“orphan”), especially to its reflex Old Armenian որբո- (orbo-), and sometimes considered a borrowing from the Armenian term. In his earlier work Klimov (1964) reconstructs Proto-Georgian-Zan *obol- (“orphan”), however later he doubts the nativeness of the Kartvelian terms, and this reconstruction is no longer considered in his expanded 1998 version of the dictionary. Instead, he compares with Chechen бо (bo, “orphan”), Hunzib гьобол (hobol, “guest”). Starostin connects it with controversial Proto-North-Caucasian *Hu(r)bV̆ ("orphan"), and considers the comparison with Proto-Indo-European *h₃órbʰos to be problematic.