The “Search Query Performance Report” could be useful for new terms of both positive and negative match.
It might return search phrases that we did not think of, maybe phrases that only recently occurred in our society, as languages always change. Even though Google matches your keyword, say “holiday”, with synonyms and singular/plural, it is still worth adding them to the campaign aiming to reach more people, not just the ones that type in “holiday”. We could be bidding on those words that don’t enter searchers’ minds at first to attract more people clicking at a lower cost per click, especially once that new keyword has been included in the creative. On the negative side, Google might match too many unwanted keywords, simply because the technique behind it assumes that people searching for “holiday” might mean “relaxation” or something similar. These could then be added as negatives.