Claim: The term "red light district" comes from the practice of railway brakemen leaving their lanterns on cathouse porches.
Example:[Collected on the Internet, 1996]
That's how they got red-light districts, you know. The brakemen. They'd be out at a house of prostitution, and since they were required to be findable at all times, they'd hang their red lights in the windows where they were.
Origins: The term "red light district" is said to have originated with early railroaders. The men carried lit red lanterns when they left the train so in case of an emergency the crew caller would be able to find them. These lanterns were left outside bordellos when crew members stopped to pay the ladies a visit and sometimes were brought inside to be placed in a window.
Though it is widely believed, I'm not quite sure what to make of this folk etymology. A railwayman's lit red lantern left sitting in front of an establishment could just as easily have
come to signify a saloon or a barber shop as it did a brothel. On the other hand, the lit red lantern quietly residing outside a nondescript building of unclear purpose could well have come to be seen as a discreet advertisement of what was for sale within.
Railroading has enriched our language with other, albeit more unusual, terms. Those who earn their living from the rails know that a "hoghead" is an engineer and a "gandydancer" is a maintenance employee. "Puddlejumpers" are clerks and "carknockers" are freight car repairmen. Like seafaring before it, railroading created its own unique language.
Where did these odd words come from? According to Charles Albi, director of the Colorado Railroad Museum in Golden, "Gandydancer" most likely comes from the Gandy Manufacturing Company of Chicago. They made many of the tools track workers used to lay rails. "Carknocker" goes back to the primeval days of railroading, the 1830s, when men would go along inspecting the train to make sure there were no cracks in the iron. They'd take a hammer and knock the car wheel to see if it would ring properly. The locomotive was called "the hog," because it was a big, powerful thing; thus, the engineer became the "hoghead."