Some of the information is Boop-Oop-a-Dooping full of SPOILERS. Boop-Oop-a-Doop! "Poo-Poo-a-Doo" is a scat technique that Baby Esther Jones used to use in her act. It is said to be the predecessor of "Boop-Oop-a-Doop."
Very similar to Helen Kane's "Poop" interpolations only without the "P" present on the end. Could actually deprive from Kane's "Poop." Kane was very well known in 1928 after her debut in Good Boy. Though Kane may have taken direct inspiration from Jones for the initial "scat singing" style / idea, "Poop" was very well associated with Kane, as scat singing was quite common among a number of performers. Jones however did scat sing prior to the Kane era which was circa 1925, Jones is said to have emulated "The Boop" style in a MGM Movietone, as it was popular in 1928, though she also did her "Wa-Da-Da" / "Wha-Da-Da" technique. When "Boop" or "Poop" was a popular phrase in 1928, everyone was using it in their songs.
Though Kane claimed to be originator of the "Poop" and "Poo" sounds, singer / dancer, Chic Kennedy claimed that "Poo" and "Poop" were actually stolen from her by Kane in a 1931 newspaper interview, while the both of them shared a bill, she claimed while she was ill, Kane started using her interpolations on the stage.