A couple of things to clarify in the above discussion.

A "palmer" originally meant specifically a Jerusalem pilgrim as Malcolm says, but by Chaucer's day it had broadened to mean a pilgrim to any hallowed site; Chaucer specifically mentions "Thanne longen folk to goon on pilgrimages/and palmeres for to seken straunge strondes/to ferne halwes, kouthe in sondry londes."

(Middle English was more flexible about clause order than modern English, so this means "then people long to go on pilgrimages, and palmers to distant holy sites known in various countries long to seek foreign shores...")

I mention this because the various mentions of Rome in the ballad suggest that this version of the story is occurring on a pilgrim route to Rome...even though it is of course based on a story that occurred in the Holy Land.

Second, Christy Moore's website does indeed mention John Reilly and Tom Munnelly in connection with The Well Below the Valley, just not in the lyrics area. When he sings the song, Christy usually talks for several minutes about how deeply Reilly influenced him. I have mentioned this in the other thread and wanted to mention it again here; Christy is more conscientious about mentioning traditional sources than any performer I know of similar popularity.