Mike/Michael,
I've had a good read of JR's 14 pages, mostly taken up with different versions and to be fair he states several times that he's not sure about the suggested symbolism. He obviously put in a fair amount of research but had nothing like the access we have today to broadsides, multiple international variants. He was doing the best with what he had to go on. There are several other songs which use the phrase 'foggy dew' for instance which he was obviously unaware of. I'll check out the earliest version of TFD as opposed to Bogalmaroo and compare this with other known Foggy Dews and report back.