A 'fly head' is used to describe someone's testicles that are bigger than their penis. The testicles represent the fly's large eyes, and the penis represents the thin/small mouth of the fly, thus being called a 'fly head'.
person#1: Haha look at James, his balls are so fucking big it looks like he has a camel toe.
person #2: Yeah, i reckon it looks a bit like a fly head.
Fogey/fogy /fougi/ sl. (early 18C+, orig. Scot) old-fashioned, stuck-in-the mud.
Person with old fashioned ideas which he is unwilling to change: Come to the disco and stop being such an old fogey!
You think me an old fogeyand an old tory, his thoughtful voice said. I saw three generations since O’Connel’s time. I remember the famine. Do you know that the orange lodges agitated for repeal of the union twenty years before O’Connel did or before the prelates of your communion denounced him as a demagogue? You fenians forget some things. (James Joyce, Ulysses. PenguinBooks,1992. p. 38)