Green’s Dictionary of Slang

goat-fucking adj.

a euph. for motherfucking adj.

1960		H.S. Thompson letter 22 March in Proud Highway (1997) 209: I would give at least one ball for one [...] of your sandwiches right at this goat-fucking instant.
1992		R. Marcinko Rogue Warrior (1993) 211: Those sorry motherfucking cocksucking pencil-dicked shit-for-brains pus-nuts goatfucker assholes.