But there was a medical condition recognized by medieval authorities that might cause normally heterosexual women to become lesbians. It was called ragadiae. According to Carolyn Dinshaw, who is your go-to scholar for weird medieval sexuality, William of Saliceto’s 1285 Summa conservationis et curationis or “Bumper Book of Treatments and Cures” defines ragadiae as fleshy growths, often in the shape of a penis, caused by difficult childbirth, other abscesses of the womb, or sometimes friction from excessive sexual intercourse. Women who found themselves in possession of these growths would sometimes subsequently develop a desire to use them to have sex with other women.

http://gotmedieval.blogspot.com/2007/07/if-medieval-lesbians-dont-get-you-back.html