Almut Hintze, The Cow That Came from the Moon: The Avestan Expression māh- gaociθra-

It is argued that the syntactic combination of ciθra- with the ablative case in the Avesta warrants the meaning "origin, offspring" and that such meaning is also present in the phrase māh- gaociθra- "the moon that holds the seed of the animal." This and other evidence indicates that the Middle Persian myth about the lunar origin of the numerous animal species on earth goes back to the Avesta.