The slinky was invented by a mechanical engineer named Richard James.

In 1943, James noticed that a torsion spring that fell off a shelf
began to bounce around with some unusual twists and turns. He took
the spring home to his wife Betty and showed her the spring’s unusual
behavior. He decided he could make the spring action into a toy and
began working on selecting the right spring steel for the coil. It
takes about 80 feet of wire to make a 2” slinky.

James’ wife came up with the name by looking in the dictionary for
appropriate words to describe the slinky action.
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Other toy question . . .

What is the longest running unchanged plastic molded toy (with a
display) that has no CRT, LCD or LED screen?

Etch-a-sketch, and it’s still around! (By the way, I read somewhere
That the Vu-Master stopped production awhile ago.)

When I was a kid, I was lucky enough to own an Etch-a-sketch,
Vu-master and Slinky.