Source : Webster's Revised Unabridged Dictionary (1913)

Sesame \Ses"a*me\, n. [L. sesamum, sesama, Gr. ????, ???: cf. F.
   s['e]same.] (Bot.)
   Either of two annual herbaceous plants of the genus {Sesamum}
   ({S. Indicum}, and {S. orientale}), from the seeds of which
   an oil is expressed; also, the small obovate, flattish seeds
   of these plants, sometimes used as food. See {Benne}.

   {Open Sesame}, the magical command which opened the door of
      the robber's den in the Arabian Nights' tale of ``The
      Forty Thieves;'' hence, a magical password.

   {Sesame grass}. (Bot.) Same as {Gama grass}.

Source : WordNet®

open sesame
     n 1: any very successful means of achieving a result
     2: a magical command; used by Ali Baba