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®

zed
     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}, {zee}, {ezed},
          {izzard}]

Source : Free On-Line Dictionary of Computing

Zed
     
        1978.  Software Portability Group, U Waterloo.  {Eh}, with
        types added.  Similar to {C}.  Implementation language for the
        {Thoth} realtime operating system.  Added a few simple types
        for greater efficiency on byte-addressed machines.  String
        constants in case statements.  Enforces the naming convention:
        MANIFESTS, Externals and locals.  "Porting the Zed Compiler",
        G.B. Bonkowski et al, SIGPLAN Notices 14(8):92-97 (Aug 1979).