Whether it’s “Ups-a-daisy,” “Whoops-a-daisy,” or “Oops-a-daisy,” you are speaking loving nonsense, usually to a child.
“Up-a-dazy” dates back to 1711, and by 1862 it had mutated into “Up-a-daisy,” spelled the same as the flower.
The original meaning was an encouragement for a child to get up, and dazy was an endearing reference to lazy, an abbreviation of lackadaisical.