Genitives in -ais (and -ai) from io -stems are assumed to contain *-ois, the ending of the IE i -stems. Attention is directed to the same meta-plasm in Oscan-Umbrian. Messapian -aihi, etc., may continue *-ois-i, and contain a double genitival ending, if the last syllable is to be connected with the genitival -ī of Latin and Celtic.
Louis H. Gray (Sun,) studied this question.
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