I have carried out a pretty comprehensive study of Streams/Strands which is in the Dungbeetle articles on the Mustrad website. The Strands of Magilligan did indeed have its origins in northern Ireland and its progress through the hands of various printers and oral tradition can be traced in ever changing forms from Liverpool to Manchester to Birmingham and then to the southern counties by when it had become a rather garbled 'Streams of Lovely Nancy'. Eventually once scholars started studying the song they came up with a whole load of weird and wonderful theories as to what it meant.

This is one of the few where I wouldn't hazard a guess as to whether it first surfaced in print or was written by some hedge poet, perhaps both.

Matt, try rereading p13.
Jim, avoid this page at all costs.