A mispelling of a the term "Bah Fungoo" apparently, wich is an term invented by Americans for a slang/dialect form of the Italian "Vaffanculo".
Bah Fungoo is in no way how it's said or spelled.
-What was that italian expression to tell you to fuck off?
-Bah Fungu? Bah Fungoo!
-Nah, neither, that's not italian at all.
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)