For reasons I can’t imagine, Americans had a fad for baby talk after WWI. That etymonline link puts “icky-boo” around 1920. Helen Kane became famed for her baby talk routine and “boop-oop-a-doop” catchphrase, which spawned the Betty Boop of cartoons.
Dorothy Parker spoofed Winnie the Pooh with:
“And it is that word ‘hummy,’ my darlings, that marks the first place in The House at Pooh Corner at which Tonstant Weader Fwowed up.”
It lasted quite a while. In the 1932 Horsefeathers, college widow Connie tries to sweet talk college president Groucho into revealing football secrets.
Connie: “If icky baby don’t learn about the football signals, icky baby gonna cwy.”
Professor Wagstaff: “If icky girl keep on talking that way, big stwong man’s gonna kick all of her teef wight down her fwoat.”