The closer to the ground, hence lower, of the two anatomical features whose resident organs govern a man's decision-making; his crotch.
By metaphorical extension, a man's head is his upper house of parliament, which in some cases vetoes the ill-conceived impulses of the lower house but is can be overruled by a super majority in the lower house declaring a state of "gots-to-have-it".
A: You see that disaster Bob went home with?
B: Yuuup, he definitely let his lower house of parliament decide that one.
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. Penguin Books,1992. p. 38)