Harry McNaughton: You know, somebody called me on the phone the other night, I couldn't understand a word they said."It Pays To Be Ignorant," December 7, 1945.
George Shelton: Why was that?
Harry McNaughton: It was a French phone.
So the "French Phone" term was still in use in the '40s. But since McNaughton and Shelton were old Vaudeville performers, the joke just might have been incredibly old, though the audience still laughed.