Foremost: look at your secondary sources and see what types of primary sources they use!
Then wrote out your topic again, but this time try find terms people might have used during the time period you're studying.
Most Important tip: USE AS FEW TERMS AS POSSIBLE.
The more search terms you use, the more likely you'll use an anachronistic term. Keep it simple, no more than 2 or 3 terms at once.
Some search terms you can use to find primary sources in the catalog: