I just stumbled upon an interesting tool of Google called: Book Ngram Viewer.
Using this tool you can compare how words have appeared in books. It measures the density of words in books.
In the above chart we can see how the use of terms like religion, medicine, soul etc… have been used in books over the last hundreds of years.
Using the chart above we can see that Religion and Spirit were popular concepts until about 140 years ago but are picking up again since roughly 1980. At least in the English language.
Defintion of n-gram
An an n-gram is a word coming from machine learning meaning a contiguous sequence of items from a given sequence of text or speech.
Any combination of syllables, letters, words regardless of the NUMBER of individual syllables, letters and words can count as an n-gram.
The n is a symbol from math and represents any NUMBER like 1,2,3,4 etc.. which hasn’t been specified.
-gram comes from Greek and means something written down – an example would be the telegram.
So this tool compares different combinations in relation to others as they appear in books.
Since the number of books have increased in the latest years, the data is compared to the number of books and words written in general.
That means that while a word like say “religion” can be shown to have a diminishing number of usages in books while is actually being used more often than in previous years.
That is because he number of books being published are increasing but so is the diversity the subjects.
However it definitely shows the comparative value of subjects over the course of time.