"Open Sesame" (French: Sésame, ouvre-toi) is a magical phrase in the story of "Ali Baba and the Forty Thieves" in One Thousand and One Nights. It opens the mouth of a cave in which forty thieves have hidden a treasure.
The phrase first appears in writing in Antoine Galland's Les Mille et une nuits (1704–1717) as Sésame, ouvre-toi (English, "Sesame, open!"). No earlier oral or written version of the story is known in any language.
Galland's phrase has been variously translated from the French into English as "Sesame, Open", "Open, Sesame" and "Open, O Simsim".
Open Sesame has been classified by Stith Thompson as motif element D1552.2, "Mountain opens to magic formula".
In the story, Ali Baba overhears the 40 thieves saying "open sesame". His brother later cannot remember the phrase, and confuses it with the names of other grains (becoming trapped in the magic cave).
There are many theories about the origin of the phrase. Indeed, it is not certain that the word "sesame" actually refers to the sesame plant or seed.
Some older theories include: