In this paper, I argue that the Semitic kinship terms *ʔab-‘father’, *ʔaḫ- ‘brother’, and *ḥam- ‘father-in-law’ originally ended in a w, which left traces in several of their forms. In the singular, the w contracted with the case vowels leaving a distinctive pattern of short and long vowels in the unbound, bound, and suffixal forms. In the plural, the w was retained in several languages due to the insertion of an a-vowel between the final two root consonants, a common Afro-Asiatic pluralization strategy: *ʔabw- > *ʔabaw. I further suggest that the West Semitic plural morpheme -aw was derived by analogy with the plurals *ʔabaw and *ʔaḫaw, and is not, as commonly suggested, an inherited Semitic or Afro-Asiatic plural marker.
