"the final cessation of the monthly courses of women," 1852 (from 1845 as a French word in English), from French ménopause, from medical Latin menopausis, from Greek mēn (genitive mēnos) "month" (from PIE *mehnes- "moon, month," from root *me- (2) "to measure," via the notion of the moon as the measurer of time) + pausis "a cessation, a pause," from pauein "to cause to cease," a word of uncertain etymology with no certain cognates outside Greek [Beekes]. Earlier it was change of life (1834).
It forms all or part of: amenorrhea; centimeter; commensurate; diameter; dimension; gematria; geometry; immense; isometric; meal (n.1) "food, time for eating;" measure; menarche; meniscus; menopause; menses; menstrual; menstruate; mensural; meter (n.1) "poetic measure;" meter (n.2) unit of length; meter (n.3) "device for measuring;" -meter; Metis; metric; metrical; metronome; -metry; Monday; month; moon; parameter; pentameter; perimeter; piecemeal; semester; symmetry; thermometer; trigonometry; trimester.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit mati "measures," matra "measure;" Avestan, Old Persian ma- "to measure;" Greek metron "measure," metra "lot, portion;" Latin metri "to measure."
1620s, "a critical stage in human life, a period supposed to be especially liable to remarkable change with regard to health, life or fortune," from Latin climactericus, from Greek klimakterikos "of a critical period," from klimakter "rung of a ladder" (see climax (n.)).
By some, held to be the years that are multiples of 7 (14, 21, 28, etc.), by others only the 3rd, 5th, 7th, and ninth periods of 7 years (21, 35, 49, etc.), to which some added the 81st year. By still others it was regarded as the years that were multiples of 9. The greator grand climacteric,supposed to be especially remarkable, was the 63rd year (7x9) or the 81st (9x9).
In 19c. medicine it often especially meant "menopause." Climacteric was used earlier in English as an adjective, "pertaining to a critical period or crisis" (c. 1600; climacterical in this sense is from 1580s).