The Collaborative International Dictionary of English v.0.48:

Whap \Whap\, Whop \Whop\, v. t. [imp. & p. p. Whapped; p. pr.
   & vb. n. Whapping.]
   To beat or strike.
   [1913 Webster] Whap

The Collaborative International Dictionary of English v.0.48:

Whapping \Whap"ping\, Whopping \Whop"ping\, a.
   Very large; monstrous; astonishing; as, a whapping story.
   [Colloq.]
   [1913 Webster]