According to Walker
a, "Alma mater," in early Roman religion, was "Soul Mother," a Roman teaching priestess, particularly one empowered to instruct in the sexual Mysteries.
Most likely, Walker is referring here to the cult of Magna Mater, an ancient Anatolian goddess also known as Agdistis, Cybele, Kybele or Kybebe. (Also, in Walker's view, related to Cowrie). The cult of Magna Mater was brought to Rome officially in 204 B.C.E., during the war with Carthage, on advice from the Delphic Oracle and a separate reading of the Sybilline Books. The cult of Cybele (or M.M.) was among the most popular in Rome, and spread throughout the empire. There are those who see definite links between this cult and at least certain sects of early Christian gnosticism, as well as strong similarities between the veneration of Cybele as mother goddess and that of Mary the Virgin Mother of Christ.c
Walker further claims a link exists between alma mater and Al-Mah, a Hebrew (and Arabic?) name for the Moon Goddess, and a title often shared by temple priestesses who served (or represented) this goddess. These women were known as almah, a word also applied to the Virgin Mary in Hebrew versions of the Christian Gospels. The priestess called alma mater had a similar relationship to male initiates as does the Tantric Shakti.
Walker's primary cited source in this is Braschb.
Apparently much was lost in translation between late antiquity and the founding of present-day colleges and universities.
Walker also suggest that Alcmene, the virgin mother of Heracles, is of related origin, and on this point, especially regarding the strong parallels between aspects of the legends surrounding Jesus in Christianity and the various heroes of the Eleusinian and Mithraic mysteries, there is fairly broad agreement among contemporary scholars.
Other sources c, d offer support for Walker's interpretations but are not entirely in agreement. This node remains open to revision and amendment, given sufficiently persuasive research and scholarship. I am also hoping to find relevant material in David Noble's A World Without Women, his study of monasticism, its links to the evolution of the Western idea of the university, and the implications that evolution had for the rôle of (and sometimes the exclusion of) women in Western academia, that is, once I relocate my copy of Noble's book.
a Barbara G. Walker. The Woman's Encyclopedia of Myths and Secrets (1983)
b R. Brasch. How Did Sex Begin? (1973)
c Adkins & Adkins Dictionary of Roman Religion (1973)
d Ann & Imel Goddesses in World Mythology (1973)