Passengers will please refrain is on mudcat. (UK trains too, up to a few years ago).

More seriously, there have been a series of accidents involving children being badly injured or drowned when caught by the suction from bathing-pool drainage ducts. This link describes one such case.

In the days of communal wash-houses, sinks and drains were built on a much larger scale than you would find in a modern house. Somebody in the case linked above suggests that these accidents are so bizarre-sounding as to be thought "urban legends" - sadly they are all too real, and similarly there may indeed be some incident that preceded the "gorn dahn the plughole" song.

Ross