An article by W. Saunders in The Nautical Magazine of August 1929 apparently traced Fiddlers' Green back to a corruption of Locus Fidelis in Gremio; a place to which sailors who died at sea without the benefit of absolution might be assigned. The piece was reproduced in English Dance and Song (vol.61, no.2, Summer 1999), having been found and submitted by Cyril Tawney. It sounds like a wind-up to me, but nevertheless the following, "paraphrased" from an account given by "a boatswain of Leith", is quite evocative:

"When sailormen die they go to a place where there is one interminable stretch of green and undulating pasture-land upon which the sun never ceases to shine, and through which fish-laden brooks and rivers dance and sparkle on their way towards some infinite far horizon. Sheep, horses, cattle and other animals -for the deep-sea sailor clearly loves a beast- with their playful young, browse all around, and the atmosphere is redolent with the sweet scents of numberless flowers, and vibrant with the song of countless birds. But in this paradise no officer may ever dwell. In the midst of all this charm and beauty, there lies a mighty bottomless pit into which all officers are incontinently pitched. On the edge of the pit the sailor man may sit and contemplate, with unrestrained satisfaction, while he turns his quid or complacently puffs at his blackened clay, the seething mass of quarterdeck humanity being stirred about unceasingly by Davy Jones himself, who wields a gigantic trident specially adapted for the purpose of keeping them going. And the sailor man is not prohibited from casting an occasional pebble or jeering epithet upon any officer of his own particular acquaintance who may happen to come to the surface as the mass is stirred about.

And that, he concluded, is Davy Jones' Locker."