I was curious about the "Banks of the Devon" melody being the origin / an earlier source of Laredo's melody. My sight singing isn't what it was in college, so I transcribed the melody found in Scottish Musical Museum, Vol. 2. There are definitely phrases in the B section that sound similar, and I could see how Laredo's melody could have evolved from that over a couple hundred years.

X:1
T:The Banks of the Devon
M:6/8
L:1/16
R:Air
Q:1/8=100
K:G
B,2|E3 F A2 B3 A d|A3 D G2 F3 E D2|E3 F A2 B3 D E2|B3 A F3 E3 B, B,|
E3 F A2 B3 A d2|A3 D G2 F3 E D2|E3 F A2 B3 D E2|B3 A F2 E4 z2|
e3 B e2 g3 f e2|d3 A d2 F3 E D D|E3 B e2 g3 f e2|B3 e ^d2 e4 e2|
e3 B e2 g3 f e2|d3 A d2 F3 E D2|E3 F A2 B3 d e2| B3 G F2 E4|]