Zipf's law is related to the statistics of how word usage is distributed. As it turns out, this is also strikingly reminiscent of how income is distributed, and populations of cities, and bug reports in software, as well as tons of other phenomena that we all interact with every day.
Relevant links:
http://economix.blogs.nytimes.com/2010/04/20/a-tale-of-many-cities/
http://arxiv.org/pdf/cond-mat/0412004.pdf
https://terrytao.wordpress.com/2009/07/03/benfords-law-zipfs-law-and-the-pareto-distribution/