The Collaborative International Dictionary of English v.0.48:

Whapper \Whap"per\, Whopper \Whop"per\, n. [See Whap.]
   Something uncommonly large of the kind; something
   astonishing; -- applied especially to a bold lie. Now (1998)
   usually spelled whopper. [Colloq.]
   [1913 Webster +PJC] Whapping

The Collaborative International Dictionary of English v.0.48:

Whopper \Whop"per\, n. [Cf. Whapper.]
   1. One who, or that which, whops.
      [1913 Webster]

   2. something very large, especially a big lie. Same as
      Whapper, but the more common spelling.
      [1913 Webster]

WordNet (r) 3.0 (2006):

whopper
    n 1: a gross untruth; a blatant lie [syn: whopper, walloper]
    2: something especially big or impressive of its kind [syn:
       whacker, whopper]

The Free On-line Dictionary of Computing (30 December 2018):

WarGames
Whopper

    (Not "War Games") A 1983 film about a schoolboy
   cracker using a wardialer to try to break into a games
   company's computer and accidentally connecting to a backdoor
   into "Whopper", a ficticious C3 computer at Norad (USAF).
   He then procedes to unwittingly initiate global thermonuclear
   warfare.  Playing naughts and crosses finally teaches Whopper
   that the only way to win the game is never to play.

   IMDb (http://us.imdb.com/Title?WarGames+%281983%29).

   (1999-03-08)