The whistle stop (or whistle-stop) is originally a railroad term for a listed station or stopping place where trains do not stop unless signaled to do so by passengers or stationmasters. The purpose of this is to save time on the route at stations which have low and/or infrequent traffic. There are two possible origins for the term - the first is that the train would usually signal its approach to the station by sounding the train whistle, so that passengers could move out into view on the platform. The other is that some references indicate that the station itself would sound a whistle or other signal in order to indicate that the train should stop.
The term later came to mean any quick intermediate stop during a journey.