The term "period" in reference to menstruation dates from 1822 and means an "interval of time" or a "repeated cycle of events."Another word for menstruation is "catamenia," from the Greek katamenia (kata = by + menia = month). A "catamenia cup" is a firm, flexible cup worn inside the vagina to catch menstrual blood.Menstruation may have led to humanity's sense of time as most early lunar calendars were based on the length of a women's menstrual cycle.Some...