Want to see how often a word is used in books by year? Books.google.com has something called an Ngram Viewer that lets you see how often a particular word or phrase in used across the centuries. There are some surprises: rifle appears surprisingly often in the seventeenth century, then falls off, coming up in frequency in the nineteenth century. Of course, remember the limitations of those OCRed books--there are a lot of words that do not appear because the print was hard to OCR.
The other limitation is that the starting date of many series is used for publication date, even if the issue in question is centuries later (or even wrong). For example, the Ngram for the word "feminism" had matches in the early seventeenth century but nothing until the twentieth century. What are those early matches? One is an error on the Latin word "feminis" in the Malleus maleficarum de Lamiis (and for all I know, it might even mean the same thing, since I think this is a Latin work on witchcraft) and the other is from Chemical Abstracts, vol. 87. I am sorry, but I do not believe that Chemical Abstracts series really starts in 1620!