How to write Irish names properly

People might have noticed that some Irish surnames are written with an apostrophe and some are not, take for example O'Donnell and Ó Domhnaill. The apostrophe does not belong in Irish here and it is lamentable that Irish people do not know this. The 'ó' means 'descendant of' . Irish people greet the the Irish version with aversion and try to translate it as they cannot accept that other Irish people want their name in the original Irish.
Mac means 'the son of' an dis sometimes anglicized as "Mc" which loses all meaning. Several thousand Irish dropped the 'o' and  'mac' from their names when they went to America so their names would appear less Irish. the old families are believed to have a banshee attached to them. An old poem went as follows:

Per O' atque Mac, veros cognoscis Hibernos;

His duobus demptis, nullus Hibernus adest.

Which has been translates as

"By Mac and O' you'll always know

True Irishmen, they say:

But, if they lack the O' or Mac,

No Irishmen are they