May I point out that the word knick-knack might be just a word? We speak of knick-knack shelf as a place to put little things and memorabilia. It is said that even Freud said "sometimes a cigar is not a symbol, just a good smoke". But for those looking for symbolism there is the "ring around a rosie" that was probably a game from the Black Plague as it describes the symptoms, then the attempted cure (posies), and the result (we all fall down). My opinion is that Knick-knack Paddy whack is a rhyming sound rather than a meaning, but that is a guess.
Best, Jon
