Douglas Harper's Etymology Dictionary
Piggly-Wiggly
chain of self-service grocery stores, started 1916 in Memphis. According to founder's reminiscence from 1921 arbitrary coinage, simply "something different from anything used before" ["Current Opinion"].
Usage examples of "piggly-wiggly".
In its stead he hastily gummed down two Piggly-Wiggly tortillas wrapped around some tiny Vienna sausages, made sure a full book of food stamps was stashed safely in his inside breast pocket, and then from a peg driven into the mud wall over his bed he removed a cracked leather gun belt and holster, which he buckled around his skinny waist.