One of the dafter claims in Daniel Cassidy’s daft book, How The Irish Invented Slang, is the claim that the word ‘Mick’, which is used in various English-speaking countries as a racist insult against the Irish, comes from the Irish word mic, the plural of mac meaning son. Cassidy doesn’t explain why this should be the case, why racists would use a word meaning son (which is usually a mark of affection), in the language of the people they were denigrating, or why a plural word would be used as a singular. Mic sounds like Mick, so it must be the origin of the word, right? Never mind that everybody in Ireland knows full well that certain common names among the Catholic Irish have become slang terms for a Catholic Irish person – Taig (Tadhg), Tim (used in Scotland), Paddy and Mick. Never mind that all of the (genuine) dictionaries are in agreement about this.
In fact, in exactly the same way, our Irish ancestors used terms like Bhullaí (=Wully or Willy) for the Ulster Planters from Scotland. For example, Art Mac Cumhaigh wrote “Bhullaidh is Jane ag glacadh léagsaidhe Ar dhúithchíbh Éireann” (Wully and Jane taking out leases On the territories of Ireland.) And one version of Úirchill an Chreagáin has the lines: Nach mb’fhearr duit ins na liosa agus mise le do thaobh gach neoin, Ó, ná saighde clann Bhullaí bheith ag polladh faoi do chliath go deo? (Wouldn’t you be better off in fairy mansions with me by your side every afternoon, Oh, than the arrows of the foreign settlers forever piercing your side?) And seoinín (=Little John, later anglicised as shoneen and jackeen) was used for people who aped English ways.
So, the likelihood is that Mick is like Paddy, Taig and Tim, a common name among Irish Catholics which was then used as an ethnic slang term, just like taffy (from Dafydd), jock (a lowland Scots form of Jack) or dago (from Diego). As usual, Cassidy’s claim is self-deluding, childish nonsense which simply ignores real and obvious derivations in favour of meaningless phonetic similarities.
However there is one other theory (apart from Cassidy’s). I didn’t mention it before because you would need to be a complete and total moron to believe it. This is the idea that Mick came about because the Catholic Irish had distinctively Catholic Irish names beginning with Mac or Mc. Anyone of normal intelligence who thinks about this for five minutes will realise that it’s crap. Out of the hundred most common Irish surnames, only thirteen of them are Mac/Mc surnames. In Scotland, the figure for Mac/Mc surnames is about the same, and you only have to look at the lists of UVF and UDA men on Wikipedia (Sam McClelland, John McKeague, Jackie McDonald, Billy McCaughey, John McMichael, Stephen McKeag etc.etc.) to realise that Mac/Mc names are just as common in the Loyalist and Protestant community as they are among Catholics, so how could Mac/Mc surnames ever have become associated solely with Irish people or with the Catholic community? This claim is so stupid, to believe it you would need to be a total airhead who’s just floated down the Lagan in a bubble!