Before end-of-semester madness, I was looking at how shifts in vocabulary usage occur. In many cases, I found, vocabulary change doesn't happen evenly across across all authors. Instead, it can happen generationally; older people tend to use words at the rate that was common in their youth, and younger people anticipate future word patterns. An eighty-year-old in 1880 uses a world like "outside" more like a 40-year-old in 1840 than he does like a 40-year-old in 1880. The original post has a more detailed explanation.
Will had some some good questions in the comments about how different words fit these patterns. Looking at different types of words should help find some more ways that this sort of investigation is interesting, and show how different sorts of language vary. But to look at other sorts of words, I should be a little clearer about the kind of words I chose the first time through. If I can describe the usage pattern for a "word like 'outside'," just what kind of words are like 'outside'? Can we generalize the trend that they demonstrate?