I learned his word for that last car on trains eighty years ago, always the last car or long freight trains. They were typically painted red, and had a low turret with windows from which the brakemen could watch the whole train ahead of them, watching for smoke indicating a "hot box" meaning failure of lubrication of the bearings of one of the wheels, with overheating and danger of collapse of the end of the axle of the wheel, capable of causing derailment.
But a few months ago, I encountered "caboose" meaning a temporary structure on deck of ships containing the cooking ovens.

AHD4 seems to indicate that the railroad train usage is derived:

http://www.bartleby.com/61/69/C0006900.html

Dear Faldage: I had completely forgotten the cooking facilities in the caboose. It now seems obvious that this is what gave it that name.
Remembering commuting by train in the days of steam, I just remembered that this was where I learned the Doppler effect. A passing train that started blowing its whistle just before it started to pass, and kept it up until it was past made the unforgettable "Eeeeeeeeeeeee-ooooooooooooooo".