Theories Abound.

Johannes Petrus Ericus assumed that Adam had named each animal by a name that reproduced the sounds that each emitted; then he elaborated a rather credible phonological theory identifying classes of letters such as 'per sibilatione per dentes,'...'per contractione palati,'...'per respiratione per nares.' Ericus concluded that Adam used vowels for the names of the birds of the air, semi-vowels for the names of the beasts of the fields, and mutes for the fish. This rather elementary phonetics also enabled Ericus to deduce the seven notes of the musical scale as well as the seven letters which designate them...

The Search for the Perfect Language, Umberto Eco.