Hmmmm… niggard | Etymology, origin and meaning of niggard by etymonline
Reports the root as “niggard” (stingy person) or “nig”
When compared to Niggle Niggle Definition & Meaning | Dictionary.com
they appear to have the same root.
Dictionary.com has this to say
USAGE NOTE FOR NIGGARD
The words niggard and niggardly are often misinterpreted as racial slurs because they sound like what is probably the most offensive word in the English language. Actually, niggard dates back to Middle English. The first element nygg-, nig- was borrowed from a Scandinavian source, and -ard is a pejorative suffix. The adjective and adverb niggardly is a modern English formation from niggard. Historical linguists and others familiar with the etymology of these words know that they are not truly related to the word nigger. However, the source of a term is not as important as how it is perceived and used in contemporary language. So even if the words niggard and niggardly are not racial slurs in their etymologies, meanings, or historical uses, it may be wisest to avoid these terms. The connotation or perception of any word is determined by how it is used, received, and interpreted; niggard and niggardly may be offensive to many speakers because of this speculative, but false, etymology.
The board is telling me we’ve had this discussion before -
and in reality I would avoid the term in most situations as communication is far more important than correctness. It still galls however when “proper” words are denied us due to ignorance.