How to locate words that were used when writing a period piece

I accidentally discovered that Google charts the popularity of terms by year!

For example, in Google, type: Sweat define

You’ll see this:

My period piece takes place in the 1850s. The word “sweat” was not commonly used. So I look at the synonyms listed in that google search:

I try “perspire”:

Much better!

I feel like I found a gold mine! Well, a “word mine!”