Complex sentence: The philosophic school of pragmatism dates back to the early 1870's, when the ordinary usage of the term "pragmatist" meant a person who meddles in the affairs of others (a busybody).
Split into simpler sentences: The philosophic school of pragmatism dates back to the early 1870's. One of of the meanings of the word "pragmatist" in the 19th century was a person who meddles in the affairs of others (a busybody).