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.
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
Just fyi, your posts in this thread are getting passed around on chan sites and are getting dozens of (You)s, I didn't start it. Don't try to delete they were using archive links and screenshots.
It's absolutely deserved. You're talking about a term for an aggressive personality that is sometimes related to a DSM classification that's a lot closer to psychopathy than, say, autism or schizophrenia when it comes to carrying a stigma, having symptoms which interfere with life & socializing.
Eh, I don't mind being 4chan's "lolcow" or whatever other ableist bullshit they've invented this week if it means I'm making radical queer identities more visible and making more common queer identities seem more normal. I mean, Trump singlehandedly normalised fascism in the US by being such a fascist clown. Maybe I could go a little way to being the opposite of that. Let them parade my identity around in front of everyone, that's what we did ourselves at Stonewall and we ought to be doing it more often.