I was always told that Minogue was the Gaelic form of Mannix, and that both trace their origin to the Isle of Man. I have no idea what that is in Gaelic. I suppose we are all variants of Manx.

My late father William Mannix (he would have been 100 on Monday!) and my late uncle John Mannix are two sons of Patrick ("Paddy") Minogue of County Clare. But this Paddy was born in 1870, emigrated to NYC in 1900, and died in the 1918 flu epidemic. Good luck on your quest!