Source : Webster's Revised Unabridged Dictionary (1913)

Zed \Zed\, n. [F., probably through It. zeta, fr. L. zeta. See
   {Zeta}.]
   The letter {Z}; -- called also {zee}, and formerly {izzard}.
   ``Zed, thou unnecessary letter!'' --Shak.

Source : WordNet®

zee
     n : the 26th letter of the Roman alphabet; "the British call Z
         zed and the Scots call it ezed but Americans call it
         zee"; "he doesn't know A from izzard" [syn: {Z}, {zed}, {ezed},
          {izzard}]