If you enjoy reading about the origins of words and phrases, you might like Wordorigins.org. Understanding why we use phrases such as "bats in the belfry" or why we drink "cocktails" is an interesting pastime. Although some of the words and phrases are somewhat outdated, it does give an interesting linguistic history of most of the more common ones. Reading this can help one understand the development of word usage over time.
What used to be unacceptable becomes common place when used by enough people.