late 14c., from Old French incantacion "spell, exorcism" (13c.), from Latin incantationem (nominative incantatio) "art of enchanting," noun of action from past participle stem of incantare "bewitch, charm," literally "sing spells" (see enchantment).
Any particularly arbitrary or obscure command that one must mutter at a system to attain a desired result. Not used of passwords or other explicit security features. Especially used of tricks that are so poorly documented that they must be learned from a wizard. "This compiler normally locates initialised data in the data segment, but if you mutter the right incantation they will be forced into text space."