Last week, there was a post on H-Sci-Med-Tech asking for colloquial terms for menstruation for a colleague who is writing a historical novel set in the mid-twentieth century. I immediately thought of Anne Frank’s reference to her “sweet secret” in her diary, as well as Judy Blume’s Are you There God, It’s Me, Margaret. One reply mentioned “my friend is here” and “fell off the roof.” I did a quick Google search and found an extensive list here. Then the Onion has a nice little top nine list. I doubt any of these are what this person is looking for, though. Maybe this is one for the guy at the Museum of Menstruation.
Knitting Clio
Knitting Clio 
The query was actually for a historical novel set in the mid-19th century–but given the replies on H-Sci-Med-Tech (like “fell off the roof”), others misread it as mid-20c. too.
Offlist, I forwarded Dan some from before 1820, but I suspect those were too early for the purpose. They were mostly variations on “indisposition” and “my usual complaint.” But “the crisis expected on every lunar change” is in a favorite 1810 letter, in which a male schoolmaster is trying to explain to a 13yo girl’s male guardian what’s really troubling her health. (The girl’s aunt concurs: “She makes her indisposition sometimes a pretext to prevent her perusing her studies… you may tell her I think so, because I have witnessed the thing often.”)
Thanks for correcting my mistake, Penny!