You are the only person that has made me curious about the family name. My grandfather Michael b 1846 and his brother Patrick born 1839 and a third brother who possibly was named John and for whom I have no info came to the US in the 1850's as teenagers. Mike and Pat came to Illinois while the third brother stayed in the east. They came from County Clare. Oh, and we spell the name Manyx. Of course I do not know what the third brother might have used. I had thought with the internet I might find him but no luck. I have a letter from their Aunt Bridget Minogue from (can't read) Hospital, Scariff Union, dated 18 Nov 1894 and a letter from their mother from Derilk dated 07 Mar 1876 signed Mary Minogue. I have had no luck anywhere to find anything. I have been to Ireland twice. The first time I met a man with whom I had been corresponding who claimed to know about my family and be a very distant relative. The last time I was there in 2001 he was no longer living. His name was Paddy Purcell. I cannot be certain of his info.
As you are aware the name seems to be interchangeable with Minogue. And I have read several reasons that it depended on what part of Co Clare you came from, but it does not address why the name would change from father to son. Anyway, I suppose we might be distant cousins. Everyone else who has ever contacted me has not had ancestors that came from Co Clare or Scarriff. My tree is Manyx Family Tree and it is public if you want to check anything on it.
My grandfather died in 1896 when my father was only 10. So the info about the family was pretty scarce. My father married late in life and by the time the internet came along he was no longer living. Through the years I have gathered any info that I could from notes I made along the was with my fahter and his brothers and sisters, but other than a letter that says they corresponded with the family in the east I have never had much evidence to go on. The letter just says there were several members in the east. Good luck with your searching.