A `stagecoach` was a large closed carriage pulled by horses that carried paying passengers, letters and parcels along a fixed route, on a fixed timetable. Before trains, this was public transport. It ran in Britain and across Europe from the 1600s onwards, and it is burned into everyone's picture of the American West in the 1800s — the coach rocking along a dusty road, a driver up top, a guard with a gun, and somewhere in the story, robbers.

The "stage" in it is the interesting part: a stage was one section of the journey, from one inn to the next, perhaps ten or fifteen miles. At each stop the tired horses were swapped for fresh ones and the coach went on. The journey was made of stages, so the coach was a stagecoach. That is also why we still say a journey is done "in stages".

Today the word is purely historical — nobody rides one to work — so you meet it in old novels, in Westerns, and in museums. In Britain, Stagecoach is also the name of a large modern bus company, borrowing the old image on purpose.