GreenWhiteBlue & panjandrum,
I agree with panjandrum in saying that "we could, of course, be mistaken." and in fact yes the use of
derry-o in the lyrics of the American version of
Farmer in the dell could be nothing more than lilting or diddling non-lexical vocables.
However, it seems like too much of a coincidence that two separate geographical toponyms that both describe wooded areas: 1. a dell (a small wooded valley), and 2. a derry (an oak grove and/or an area densely wooded with oak trees), would just happen to appear in the same rhyme but yet only one carries a lexical semantic meaning and the other is just filler.
GreenWhiteBlue you say that I have
given the origin of the name of the city and county of Derry in Ulster.
I just want to explain that the anglicization of Irish
daire/
doire to derry was not just done in the case of Londonderry. There are hundreds of places and townlands throughout the whole of Ireland that are named Derry or whose name includes the word derry. These places and townlands are not named after Londonderry. They are so named because at one point in their history their original local Irish name included the geographical toponym
daire/
doire. Quick example, I know of six places named Derryfadda which originally were
Doire Fada (which in Irish Gaelic means long oak grove).
panjandrum, I complete agree with you that "there is no connection between this rhyme and the city of Derry." The thing is Londonderry though the biggest Derry is not the only Derry. When I suggest that
derry-o might refer to a derry/daire/doire I'm not referring to the County or City of Londonderry. I am referring to geographical toponym that refers to an area wooded with oak trees.
GreenWhiteBlue, Also while I do believe that the OED is an excellent resource, by far one of the most ample and well researched dictionary of the English language, the truth is, it's not perfect. They're a number of scholarly critics who suggest that the OED has long minimized or neglected to fully show the influence that Celtic languages have had on English. Just because the OED does not deign to trace the etymology of derry doesn't mean there isn't one.