The Collaborative International Dictionary of English v.0.48:

Izzard \Iz"zard\, n. (Zool.)
   See Izard.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Izzard \Iz"zard\, n. [Formerly ezed, prob. fr. F. et z['e]de and
   z.]
   The letter z; -- formerly so called.

The Collaborative International Dictionary of English v.0.48:

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.
   [1913 Webster]

WordNet (r) 3.0 (2006):

izzard
    n 1: 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, z, zee,
         zed, ezed, izzard]