gradation (n.)

1530s, "a climax;" 1670s, "orderly arrangement or succession," from Middle French gradation (16c.) and directly from Latin gradationem (nominative gradatio) "ascent by steps; a climax," noun of action from gradi "to walk, go, step" (from PIE root *ghredh- "to walk, go"). Meaning "gradual change" is from 1540s.