decadence (n.)

1540s, "deteriorated condition, decay," from Middle French décadence (early 15c.), from Medieval Latin decadentia "decay," from decadentem (nominative decadens) "decaying," present participle of decadere "to decay," from Latin de- "apart, down" (see de-) + cadere "to fall" (from PIE root *kad- "to fall"). Meaning "process of falling away from a better or more vital state" is from 1620s. Used of periods in art since 1852, on French model.