I've recently learned about the practice of 坐月子 or sitting the month where a woman secludes herself for around a month following a pregnancy. The articles I've read indicate that this practice has been around quite a while.
I'm curious as to when this expression first came into use and if there are many historical precedents for it.
The earliest reference i can make is a chapter "Nei Ze" in a book "Liji" (See http://ctext.org/liji/nei-ze). The word "sitting the month" has been replaced by "the month of confinement", "坐月子" by "月辰".
Sitting the month is a tradition since the Western Han Dynasty, people think women's menstrual blood and the body after childbirth is unclean. It can angered deities and bring disease and disaster, so mothers can not leave before the child is a full month out of the delivery room. Now sitting the month is treated as a necessary measure to recover from the childbirth.
