invasion Look up invasion at Dictionary.com
1439, from M.Fr. invasion (12c.), from L.L. invasionem (nom. invasio) "an attack, invasion," from L. invasus, pp. of invadere "go into, fall upon, attack, invade," from in- "in" + vadere "go, walk" (see vamoose). Invade is 1491, from invadere.