Another oft-quoted claim of Cassidy’s, which has absolutely no basis in fact, is the notion that crony can be traced back to an Irish phrase comh-roghna. Cassidy says that this word means “fellow chosen-ones, mutual-sweethearts, fellow favourites, close friends, mutual pals”.
While comh– exists and rogha/roghanna exists there is no evidence in the Irish language of either roghanna or comhroghanna being used to mean friends or pals. Comhrogha and comhroghanna are not even in Ó Dónaill’s dictionary, though the word comhrogha has been used with the senses of rival, alternative or choice. Rogha means a choice. There are plenty of words and phrases for the concept of friends or mates – cairde, compánaigh, comrádaithe. Comhroghanna and roghanna are not among them. They do not occur in the dictionaries with these meanings and they are not used in speech in this sense.
While the other words for companion or comrade, comrádaí, compánach and cara occur many times in Corpas na Gaeilge (a database of Irish), comhrogha only occurs five times and always in the sense of choice or alternative, never to refer to friends. In any case, comhroghanna (koh-ray-anna) doesn’t sound much like cronies to me!