late 14c., "pertaining to menses of females," from Old French menstruel and directly from Latin menstrualis "monthly," especially "of or having monthly courses," from menstruus "of a month, every month, monthly, pertaining to a month," from mensis "month" (see moon (n.)). Occasionally, in astronomy, "monthly" (1590s).
"having the monthly flow or discharge," early 15c., from Old French menstrueus and directly from Medieval Latin *menstruosus, from Latin menstruum "of or belonging to menstruation," from menstruus (adj.) "that happens every month, monthly," from mensis "month" (see moon (n.)).
"a crescent or crescent-shaped body," 1690s in reference to lenses convex on one side, concave on the other, and thicker in the middle; c. 1812 in reference to liquid surfaces, Modern Latin meniscus, from Greek meniskos "lunar crescent," diminutive of mene "moon" (see moon (n.)). Related: Meniscoid; mensicoidal; mensical; mensicate.
"the period of menstruation," 1680s, from past-participle stem of Late Latin menstruare, from menstruus "monthly" (from mensis "month;" see moon (n.)) + -ation. Old English equivalent was monaðblot "month-blood." Middle English had menstrue (n.), late 14c., from Old French menstrue, from Latin menstruum.