4 points
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.
English isn’t a person, it’s a language. The root word narcissism was pulled into english by people. Those people were late 19th century psychologists.
2 points
It was put into general use by a book which claimed comtemporary america was normalising NPD, and later by self help books selling the old Hitler special - all your problems are caused by a vulnerable minority and please give me money
