A quatrain ballad, this describes the sexual activities and practices of the train crew and passengers. Recognized by the internal chorus, "(She/It) blew, (She/it) blew" and the final line "How (she/it) blew."
The history of this song is a bit vague, as it has both clean and dirty forms. Sandburg prints a single stanza of a clean text (saying of it "This is for cold weather, around the stove in the switch shanty"). But the bawdy version seems to be much more widespread.
Which is original? The evidence available to me does not make it clear. The possibility that Sandburg's text is bowdlerized cannot be denied. - RBW
The Sandburg version may indeed be bowdlerized, but Vernon Dalhart also put out a clean version of "The Runaway Train" in 1925, two years before. Actually, he put it out several times that year, on different labels. Sandburg's verse isn't on his recording(s), though. - PJS