illusory (adj.)

1590s, from French illusorie, from Late Latin illusorius "ironical, of a mocking character," from illus-, past participle stem of Latin illudere "mock, jeer at, make fun of," literally "play with," from assimilated form of in- "at, upon" (from PIE root *en "in") + ludere "to play" (see ludicrous).