Market research

"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 over the selected years." (Google Ngram)

"You can use Google Books Ngrams to find out what topics and keywords are trending or declining over time. For example, you can compare the popularity of different genres, authors, products, or concepts in different periods. This can help you identify relevant and timely topics for your content marketing." (Fastercapital.com)

https://books.google.com/ngrams/