I do not think that the Irish apply a veneer on a Shillelagh. A shillelagh is an Irish weapon, a fighting stick. A piece of wood, shaped in a way to be comfortably hand held. Its purpose is to hit the opponent with it. It originates in the years gone by and seems to have been quite popular amongst the Irish.

This is my shilelagh, although never used. It just looks interesting to have. I keep mine in the bedroom, you never know when you might be glad to have it.