It's not retarded. It sounds very much like a nonsense word with lots and lots of variations of it that you would say to a child - upsie-daisy,
whoopsie-daisy, up-a-daisy - and is said to a child when they've fallen over or if you've spilt something you say "oopsie-daisy". It all sounds very harmless but it actually goes back to something that is a LOT stronger and has
absolutely nothing to do with the flower the daisy.
The origin was "up a day" which in turn was a version of "a lack a day", (see the example below) and it was a heart-felt
passionate cry of anguish. For whatever reason, it became diluted over time - so diluted that "daisy" crept into it and it became "upsie-daisy". "Lack a day" also went in another direction. Again "daisy" crept in, and "lackadaisical", believe it or don't, stems from this "a lack a day" with the idea of something careless, perhaps lazy, which then in turn brings a mistake upon you. But as I say it's now a fairly flabby or acute thing we use, but it once was a very, very strong cry of torment.
