I am sure I know the butterfly you mean, and the common name begins with ‘n’, though there is another butterfly whose common name starts with ‘c’ that s equally insulting. This common name has been in use for at least 100 years, long before the word got its very bad meaning (i the 1950’s). In fact, when the word was first coined, it was a word of respect!
I understand that it now upsets many people, and I would prefer abandoning any common name, and just leaving the unambiguous scientific name. Giving a new ‘common’ name, will only confuse.