Refers to the mythical 'leader' of the Captain Swing Riots. These were rebellions by impoverished farm workers in the rural south of England, around the year 1830, when suffering was caused by farmers starting to use threshing machines instead of hand threshing with flails and thus depriving seasonal farm workers of an important source of paid work to keep them going through the winter: gangs formed and broke the thrashing machines.
In the second half of the 20th Century, the name of Captain Swing was widely invoked and celebrated by the English folk music revival.
Reference works
Captain Swing (Eric Hobsbawm & George Rude, 1969)