Why do some Jewish women shave their hair? Is there a mekor for doing so?
There are a number of reasons why those married women who shave do so. The first reason is because there are opinions who hold that a woman has to keep her hair covered even in private. Although this is a minority opinion, however there are though who hold by it, and it is very difficult to ensure that no hairs will be exposed, but shaving them ensures that her hair will not get uncovered at any time. The other reason is because of the gemora Yuma 47a, that Kimchis was exceedingly modest and her hair was never exposed even in the privacy of her own home, and she merited to have 7 sons that became kohanim gedolim. Additionally the Zohar was very strict about this that her hair should never be seen. Also the Zohar says to do this for kabalistic reasons.
Mishna Berura 75-14, Biur Halacha ibid D:H Chutz L’tzamasan, Chasam Sofer 36, Darcei Teshuva Y:D 198-91, Malbushiei Mordechai 3-10