My 1st hearing of the phrase was from Bill Halley and the Comets in a song with that name some time in the '50s*. At this point the rejoinder was "After While Crocodile". (Included in the song)
I too thought it was just a cute but empty phrase. Thanks for cluing me in.
- We may have been saying it too, but the song made it official! Still a pretty good song too... while saxes were still part of Rock and Roll before really loud guitars drowned them out. (much later they managed to properly amplify the sax without losing it's character)