The origin of the morpheme *-ai̭os occurring in some gentilicia of pre-Roman Italy attracted specific attention in the studies of personal names. It is a secondary suffix arising from merging of a thematic -a and the common *-i̭o- suffix. The remarkable frequency of *-ai̭os in a set of onomastic bases attested in a specific area of the Sabellian languages (particularly Sud-picene and Paelignian ones) since archaic time suggests that the onomastic bases at issue were responsible for the origin and diffusion of this morpheme. These onomastic bases are featured by the morpho-structural pattern aCCa- typical of 'baby talk', that in numberless world languages gave way to different kinship terms, especially basic terms such as 'father', 'mother', 'great mother', variously preserved in almost all languages of ancient Italy with both lexical and onomastic functions.