It has occurred to me that you could construct a kind of historical spell-checker that would flag words that are inappropriate to a certain historical period. The underlying data is available now that thousands of books and hundreds of newspapers and periodicals of all historic periods have been digitized.

The kind of information I mean is already available at Google to some extent. See here, for example, for graphs that shows that online use of the terms "folk song" and "folk music" has steadily declined in the last 8 years.