Thanks to Marc Demarest, yesterday I discovered this incredible new tool at Google books, which allows one to search the frequency of various words and phrases in literature over time. If astrology, Tarot, and Hermetic are our three most significant keywords, this diagram is instructive (click to enlarge):
There is a leap in astrology around 1920, just as the public work of Elbert Benjamine begins. I think we can safely assume that his prolific writing had something to do with this, in that he was riding a wave of public interest in the subject.
As for the relative significance of terms describing our source traditions, Spiritualism, Theosophy, and occultism yield the following picture over two centuries:
