late 14c., "singleness of nature, unity, indivisibility; immutability," from Old French simplicite (12c., Modern French simplicité), from Latin simplicitatem (nominative simplicitas) "state of being simple, frankness, openness, artlessness, candor, directness," from simplex (genitive simplicis) "simple" (see simplex).
The sense of "ignorance" is from c. 1400; that of "simplicity of expression, plainness of style" is by early 15c. Middle English also had simplesse, from French, and compare simpleness. The earliest was simplete, "lack of ostentation," c. 1200, from Old French.
updated on November 03, 2022