don't know when the exact phrase was first used, but Lomax used his field trip to Italy in 1954-55 to roadtest the theories about different regional singing styles that he came up with during his visit to Spain in 1952-3 (where one of things that struck him was the difference between the "long, high-pitched wails of despair" he found in the south and the open-throated, lower-pitched stuff he found in the north).

My guess is that it was after he returned to the States from London in 1958 that he formally set down his ideas of your typical Eurasian song (high-pitched, tight-throated and tragic) and brought the 'high lonesome sound' of colonial america under its umbrella.

But it's only a guess.