Christopher Ehret argues for its presence in Proto-Afroasiatic and for its attestation in some form in all branches, with a shape -*ay in addition to -*iy in some cases.
kɹˈɪstəfɚɹ ˈeɪɹɪt ˈɑːɹɡjuːz fɔːɹ ɪts pɹˈɛzəns ɪn pɹˈoʊɾoʊˌæfɹoʊˌeɪsɪˈæɾɪk ænd fɔːɹ ɪts ɐɾɪstˈeɪʃən ɪn sˌʌm fˈɔːɹm ɪn ˈɔːl bɹˈæntʃᵻz, wɪð ɐ ʃˈeɪp ˈæstɚɹˌɪsk ˈaɪ ɪn ɐdˈɪʃən tʊ ˈæstɚɹˌɪsk ˈɪi ɪn sˌʌm kˈeɪsᵻz.