Kleenex was a popular brand. It was zeitgeist or cultural momentum. It isnt clear what process would result in a self recognized legal name change of the USA.
> when did the self-recognized legal name change of tissue paper take place?
Gradually, when they didn't enforce their trademark via lawsuits / etc. There's no line in the sand at which point you lose a trademark and it becomes generic. At some point you file suit and fail, or don't even try, and "it is known".
the product formed from taking tree fiber and creating thin sheets of semi-translucent paper, frequently used with a toilet or for blowing one's nose, has no legal name.
Who proposed the name change from "tissue paper" to "kleenex"?