The word is controversial, even though it is only phonetically related to the offensive racial slur.
https://en.wikipedia.org/wiki/Controversies_about_the_word_niggardly
You are correct... it's etymology is different, and predates the racial slur by several centuries. Still, using it in certain contexts can be considered provocative and racially insensitive.
We'll leave it for now, as it could be considered educational for some. But if a complaint is received, we may need to lock the thread if it is deemed as 'trolling'.
♥