The STD in question that is left blank in the lyric above is the "Glyn":"Bad luck to the girlie that gave him the glyn"
As I understand, this is Scots for syphilis.
There is a dynamite rendition on "Half Ower, Half Ower tae Aberdour, Traditions Bearers Records, LTCD1006 by Jack Beck.
The tune is also the one to "The Road to Dundee" another Scots song. Streets of Laredo is a direct derivitive.
Wayne Bean