I heard Jimmy McCarthy been interviewed on RTE radio and when asked about the bases of the song he said that he wrote the song after a particular bout of serious illness where he needed hospitalization I'm sure he said he wrote the song over a very short time something like 1/2 hour on the back of a scrap of paper I feel Brendy has given a very good analysis of the song. Surely Jimmy is one of Ireland greatest ever poets his lyrics are just enthralling and not a bad singer either.