grapes of wrath

[NTHS@AOL.COM]

Chap. 15 of Grapes of Wrath tells of  these abbreviations on a sign in the
diner: IITYWYBAD. I'm told this stands for "If I tell you will you buy me a
drink?" Does anyone know of a source that would confirm? I've checked guides
and criticism of GW and popular culture books and language/slang guides--no
luck so far. Thanks!  reply to nths@aol.com   (Anne O'Malley)