I wouldn't. Words are borrowed or adopted from other languages. To coin a phrase is to come up with something new.
I guess words can also creep into a language.
Some German words crept into English.
"Coventrate. Verb meaning to 'utterly destroy'. Coined from the German verb 'Coventiren'."
Would this have been written wrongfully?
Nearly clicked 'Like', but it's not that simple. I like your coining - 'autoantonym', but, to coin a phrase, my lip will always curl when people do that. ;-)
b