This graph represents the use of different terminology over time (from 1700 - 2000) as found in Google Books' digitized collection (click on the image for the full size, click on the in-text link for the details of search criteria or to run your own).
Below are a series of related breakdowns.
Monster, monstrous, monstrosity:
Given that the Google Books collection is far from extensive and doesn't take into account the context of the words, to read any conclusive meaning into these graphs would be unwise. Nevertheless, they are intriguing in and of themselves.