Cadger is derived from an ancient Scottish and English term meaning a peddler. The meaning of scrounger seems to be of fairly recent origin along with the verb form ‘to cadge’.
At some stage, this was borrowed into Irish as caidéir. This is given in Ó Dónaill, but not in Dinneen. Dinneen tended not to include words which were obviously borrowings from English. Cassidy cites this word and also another word which is given in Dinneen, ceaidé, which is obviously a completely different word. How cadger could come from two completely different words is not clear. It’s like a child having two fathers. However, we’re not dealing with reasoned arguments or evidence or facts here. We’re dealing with fantasies invented by a lunatic.
The fact is, cadger is an ancient English/Scots word. There is evidence for this. It was borrowed into Irish. It is not an Irish word. In relation to this word, Cassidy was doing what he did best – lying.