The Importance of synonyms
When searching, you should always be thinking of synonyms for your key search terms and once you run out of search combinations on your primary search term, move on to your list of synonyms.
What is a submarine sandwich in one part of the USA is called a grinder, Italian Sandwich, Hoagie, and probably a few other things in different parts of the country. Irish tin whistle, fedogh, or pennywhistle? All of course. Each different author has a different vocabulary and you need to tap into their set so you can find their content.
Rely first on your own internal thesaurus, but then make sure to consult a real thesaurus such as thesaurus.com.