just a few observations: as “mammele’ writes, the hungarian minhag -al pi chassam sofer- was to shave the woman’s head because they were worried that ,during tevilah, a hair or two would float above the water (especially when they are long)and so the tevilah would not be good.
there is also a “zohar’ (mdd was kind enough to show us a mareh mokom) that equates hair as coming from the “sitra achara” -the evil side and because of that men also shave their head-apart from the peyos. Incidentally, this does not apply to the beard-obviously!
Notwithstanding this late hungarian minhag, it is clear from tenach and gemoro and rishonim that women never shaved their head prior to the nineteenth century.”lulei demistafina” – if I would not be scared on saying this, I would venture to say that this minhag originated in the eighteenth century when all kind of people- including gentiles- shaved their heads for hygienic reasons- and the Jews followed suit- with an assist from a specific chumro.