Zipf's law states that within any large body of text, a word's popularity or rank multiplied by the number of times it shows up will result in the same value.
Rank X Number = constant.
This law holds for the Bible, pop songs, and literature. Here's the law applied to James Joyce's Ulysses:
That is an absurdly robust prediction. I don't care who you are, that's abundantly cool.
Dataclysm by Christian Rudder is the source for this gem of an idea.