X to doubt on your claim there, but why does that matter? The N word and the R word existed before they were slurs too. Are you going to apply the same logic there or do you have a unique hatred for pwNPD?
You doubt that a word meaning “like Narcissus” was used to describe behaviour similar to the popular thousands of years old mythological figure, before modern psychological science used it to describe a personality disorder?
Yes. I’m also going to doubt that anybody in this thread was speaking Greek when they used the word narcissist, given that all these comments are in english.
English mugs other languages and their associated grammatical rules all the time, especially Greek and Latin, and especially especially words related to mythological figures, like Herculean, Titanic or indeed, Narcissistic.