A related word, according to my Irish slang source (http://www.loughman.dna.ie/general/4mymofo.html) is "gobdaw", which is reportedly used to mean "a fool, or an idiot". the example they use is "That fella's a right gobdaw".
Perhaps Rubrick can verify this for us ~ and while you're at it, whence "daw"?Gobdaw is mostly rural slang (not Dublinese wot I speak). Gob = mouth. Daw (duh) = idiot.
More common is the less PC
gobshite which can actually sound pretty funny coming out of the gob of a gobdaw.
Fr. Jack Hackett, a fictional character from the very popular Irish comedy programme
Fr. Ted had a vocabulary of five words - one of which was gobshite. For the correct pronunciation of this (and other words) have a look at the unofficial Fr. Ted website below.
http://www.geocities.com/ResearchTriangle/2079/ted.htm
