@bitnacht Good point, re: the busy bee.
As for the spinning disc (or "beachball"), it got its start in NEXTSTEP as a greyscale spinning magneto-optical disc rendering indicating the system is busy / data is loading, which was seen quite often on the early NeXT Cube, as it came with no HD but only an MO drive, and it used that drive for _swap_, if you can imagine...
That spinning disc became color when NEXTSTEP gained a color display on later hardware, and from there it evolved into the spinning "beachball" we know today (macOS being structurally based upon and evolved from NEXTSTEP/OPENSTEP).
EDIT: Oh, I think I misread - you are talking about the busy mouse pointer icon in Windows, I think. I'm not sure of its specific history. Apologies.