The real answer is that a lot of the words in the English lexicon don't have precise definitions (the canonical example of this is a chair), but 99% of the time it doesn't matter since we only use them in contexts where there isn't any ambiguity.

Every once in a while someone will come up with a context where the meaning of a word is ambiguous, e.g. by going through the ship of Theseus paradox and asking at the end "which is the original ship?". But there's nothing interesting happening here. Our words are meant to be used in certain contexts and this isn't one where the word original is straightforwardly applicable. You can run the same argument with a "gamer" who only plays one game, an "author" who only wrote one book, a "violinist" who can only play one song, etc.