A couple of weeks ago, someone on one of my historical fiction listservs asked if anyone out there knew when the term “smelling himself” as in “full of oneself” came about. The writer was afraid of an anachronism in a piece of dialogue she was creating for a historical novel. Someone on the listserv suggested that she try putting the phrase into Google’s N gram viewer.
According to the website, when you enter phrases into the Google Books Ngram Viewer, it displays a graph showing how those phrases have occurred in a corpus of books (e.g., "British English", "English Fiction", "French") over the selected years. You can find plenty of examples at the sites info link.
This free tool strikes me as useful for writers who want to be sure their idiomatic expressions used in dialogue are authentic to the period about which they are writing. Or perhaps you are wondering what year a certain object came into use. I tried an experiment with “seatbelt” and found that the term came into use in print (at least in the books Google searched) about 1960. You can run your own experiment at the site.