'illusionary' originates from the Latin word 'illusio,' where 'illus-' meant 'to mock' or 'to deceive.'

'illusio' transformed into the Old French word 'illusion,' and eventually became the modern English word 'illusionary.'

Initially, it meant 'to mock or deceive,' but over time it evolved into its current meaning of 'having the nature of an illusion.'