According to a 1980 DV news item, the gibberish song Chaplin
sings "stems from a classic old ribald joke about the girl who goes to
[a] pawnbroker to cash in the ring she earned by getting picked up only
to be told by him it's a fake. The tag-line, uttered by her, was 'My
God, I've been raped!'"
You can even hear the "pawnbroker" word, and everything that happens in the story is clearly seen in his pantomime.
EDIT: Okay, no "pawnbroker", but I've definitely read the lyrics where the line was there: "Les de, le ce, pawnbroka, Lee de ce peu how mucha Lee ze contess e kroke, punka wa la, punka wa". Urban legend?
EDIT2: Hey, here's this song with this line! But why is it cut in most clips, including the full film I found?