early 15c., "nimbleness, quickness," from Old French agilité (14c.), from Latin agilitatem (nominative agilitas) "mobility, nimbleness, quickness," from agilis "nimble, quick," from agere "to set in motion; keep in movement" (from PIE root *ag- "to drive, draw out or forth, move"). Of mental swiftness from mid-15c.
