The origin of the slinky is the manufacture of steel piston rings. the coil was cut evenly to produce countless perfectly uniform rings used in the construction of engines. My father was shop foreman for American Hammer Piston company during WWII. We played with these proto slinkies as children.
Yep, that's how a lot of 'toys' started out, as industrial components which were found to be 'fun' to play with ...ie: Pinball (a ball bearing
In the mid 80's I was working for an industrial component distributor as an order clerk ... all of a sudden we started to get orders for large quantities of rubber O-Rings, particularly in sizes 3-4" inside diameter. Turns out that singer Madonna had started a fashion craze by wearing O-Rings as bracelets. Those orders were coming from entrepreneurial jobbers seeking to cash in on the latest fashion fad