Nim was originally “Nimrod.” It’s probably a play on that.
Akin to one day, Einstein being known mostly as meaning 'idiot' rather than a physicist.
Look up the history of the word "nice" in England, sometime. But no, it is not just an English-speaking phenomenon, either.
Example: people think rabbits mostly eat carrots because Bugs Bunny likes to snack on them while leaning on something and saying "What's up, Doc?". Except Bugs doing that was a reference to a movie where Clark Gable... ate carrots while leaning on a fence and calling people Doc.
And somehow a parody of a Clark Gable movie turned into most people believing that carrots are a staple of leporine diets.
If that is the case, why is the misconception also widespread in countries where Bugs Bunny wasn't part of the popular culture? E.g. USSR/Russia.