Do you know why someone who regularly spends a certain amount of time traveling back and forth between home and work is called a "commuter"? It's because the first people so called were using commutation tickets, what we now call season tickets, that commuted ('changed,' from Latin commutare) a bunch of daily fares into a single payment. (If you check the foreign equivalents linked at the left of the Wikipedia article, you find that a number of languages use a word or phrase meaning 'pendulum migration.')
Never thought about that, but that makes sense.
Language is fun!