hapax legomenon unique occurrence of a word, a word that occurs uniquely, only once in the corpus of a language. Perhaps “normalcy” would have been one of those had a president not uttered it and thus inserted it into the language.
Wikipedia:
Although detractors believed that the word was a neologism as well as a malapropism coined by Harding (as opposed to the more accepted term normality), there was contemporary discussion and evidence found that normalcy had been listed in dictionaries as far back as 1857.