Some drunk lad from lets say limerick if it is so widely used there as the above person states. Must have got drinks mixed up
Fíona meaning WINE and Beor meaning BEER are usually found on the same page of basic irish books, usually in, the food and drink secion. Somehow this drunk probably in 4th class has started a tradition of calling a girl a beor (beer) and knacker(guy) a Fíon(wine).
If things were right itd be the other way around. But theres no hope.
"hes a shmelly fion"