Yours, Etc.: Origins and Uses of 8 Sign-Offs
"monthly discharge of blood from the uterus," 1590s, from Latin menses, plural of mensis "month" (see moon (n.)).
menses men·ses (měn'sēz)n. The monthly flow of blood and cellular debris from the uterus that begins at puberty and ceases at menopause. Also called emmenia, menstrual period.