This weekend everyone's playing with Google's new Books Ngram tool, which shows you how often any word you can think of showed up in books in each year of modern history, using Google's vast archive of digitized books. The tool can be set to look back to before 1600, but before 1800 or so the dataset is too small to mean much.
"Tram" vs "streetcar" is interesting. It seems that in the golden age of streetcars nobody was saying "streetcar" yet:
Then there's "bus" vs. "coach."
Personally I love the word "coach," and want it back, but I'm sure that the word's 20th century run refers mostly to athletic coaches.
You can sometimes see a change in the prevailing meaning of a word marked by a low-point in its frequency, and that may be happening to "coach" around 1920. (For an obvious recent example of the same phenomenon, see "gay.") Words go quiet for a while as nobody's sure what they mean anymore. Then people get sure, and they take off.
Few transit terms are easy to search, because the profession's vocabulary is constructed metaphorically, so almost every word we use has a more common meaning outside the transit context. But "city" and "town" are fascinating:
"City" has lost about half of its frequency in the last century. In the 19th Century, novels that took place in cities made sure you notice the fact, often dwelling on the confronting textures of city life. Cities and country are in clear opposition, and as the Industrial Revolution rages everyone's worrying over the contrast between them. The city is emerging as one of the main problems of civilization.
Then in the 20th century we get the rise of subjectivity -- the idea that stories don't really need settings if the personalities are vivid enough -- and also the rise of specialization, which means that stuff that happens in cities is less likely to credit the city as a necessary frame. And that, of course, sets the stage for the flight to suburbia and the possibility of no longer caring what a city is. But starting around 1960 there's the beginning of something new.
Of course, some of the decline in "city" matches the rise of "urban," which dances closely with "rural."
"Urban" rises as "city" declines. Before the "urban" was invented (followed not long after by "urbanism") everyone just talked about the city.
Have fun! Did you know that the word "interchange" has been in decline since 1963? Me neither!