c.1600 (adj.), 1620s (n.), from Latin climactericus, from Greek klimakterikos "of a critical period," from klimakter "rung of a ladder" (see climax (n.)). A critical stage in human life, a period supposed to be especially liable to change. By some, held to be the years that are multiples of 7 (7, 14, 21, etc.), by others only the odd multiples (7, 21, 35, etc.), and by still others the multiples of 9. The Great Climacteric was the 63rd year (7x9), supposed to be especially critical.