This is of course a coat of arms once awarded to an individual with the name Irish, and is NOT in any way a family coat of arms belonging to just anyone bearing this name. See this article about British Crests and Coats of Arms. Semper constans fidelis. The cross shows the ancestor to have been a Crusader.
Billets indicate diplomatic service to the State.
The oak indicates strength and firmness. The dragon pierced with a sword, shows that while being with courage and determination, a wound has been received with that weapon. Thanks to Jeremy Irish for scanning this image from W. Irish's book. The rooms of the Historic and Genealogical Society, Boston, Massachusetts. The rooms of the Wisconsin State Historical Society, Madison, Wisconsin.