You can remember that the prefix non- means “not” by means of the phrase nonpoisonous, for a compound which is nonpoisonous is “not” toxic. Being an interjection to negate what was reported just before or expose it as sarcasm, it really is attested by 1900, popularized 1989 by "Wayne's Globe" https://follow65319.activosblog.com/26561513/detailed-notes-on-non