There was a craze in Belfast, apparently beginning in 1945, to chalk the word (or name) "Skiboo" on walls, often under a stylized line drawing of a man peering over a wall.   Something similar happened in America beginning about 1941-42. That message was "Kilroy Was Here."

Allegedly "skiboo" was applied some years earlier to minor gangsters in Chicago, so maybe there was an earlier Irish connection.

The origin of "Skiboo" is not known; it may or may not have anything to do with the song.