Green’s Dictionary of Slang

1. a general intensifier.

1889		Texas Court of Appeals Report Vol. 28 (1890) 206: According to Sumner, he spoke of defendant as ‘that God damned lying, thieving son-of-a-bitch’; [...] and according to McKinney, as ‘that God damned mother-f——cking, bastardly son-of-a-bitch!’ [OED].
1904		‘Melton v. The State’ law report in Texas criminal reports Vol. 47 455: I asked him to take back what he had said to my wife, and he said, ‘You mother fucking son of a bitch, I will see you and her both in hell [...] before I will take it back‘.
1936		M. Levin Old Bunch (1946) 122: You mother-f– little runt.
1948		(con. 1944) N. Mailer Naked and Dead 10: Of all the mother-fugging luck.
1952		Kerouac letter 12 Oct. in Charters I (1995) 381: I start West in the rain [...] I go 3,000 motherfucking miles.
1961		R. Gover One Hundred Dollar Misunderstanding 21: Twenty berries an you alla roun the mothahfuggin worl’.
1962		(con. 1953–7) L. Yablonsky Violent Gang (1967) 82: Where are those mother-fuckin’ punks?
1964		R. Abrahams Deep Down In The Jungle 71: The lion jumped back and squared for a fight. / The motherfucking monkey jumped clear out of sight.
1978		R. Price Ladies’ Man (1985) 25: I have big motherfucking strong hands.
1985		J. Wambaugh Secrets of Harry Bright (1986) 40: You motherfucking sonofabitch cocksucker, put your hands out the window or we’ll blow your fucking face off!
1991		B. Hamper Rivethead (1992) 94: I was one blazin’ tomahawk of m-fuggin’ eel snot.
1993		Dr Dre ‘187’ 🎵 Niggas keep your hands on your motherfuckin’ shit.
1999		Guardian Guide 17–23 July 27: Nor is he likely to encourage us to ‘make some muthafuckin’ noise’.
2000		T. Udo Vatican Bloodbath 8: We got to kick the motherfucking Romans out. [Ibid.] 81: [He] was a godamn muthafucken crossdressing player of the muthafucken purple-topped pink fucken oboe.
2001		Observer 9 Sept. 10: I’ve walked a sister-fucking 20 kilometres already on this motorway, following those sister-fucking signs for the TGV. Sister-fucker!
2005		L. Theroux Call of the Weird (2006) 187: I done told you three motherfuckin’ times, no touching.
2006		B. Matthews Intractable [ebook] In that moment he was every motherfucking screw that ever bashed me.
2014		M. McBride Swollen Red Sun 130: Listen here, you cornholin’, sister-fuckin’..
2019		N. Walker Cherry 190: ‘Is that motherfucking Lieutenant Nathan?’.

2. used as an infix, to accentuate or denigrate the word thus altered, e.g. emanci-motherfucking-pation.

1972		T. Weesner Car Thief (1973) 104: Watchouttamawaymuhfuck—stompmuhfuckinassman!
1995		C. Hiaasen Stormy Weather 242: Your mangrove islands, your Everglades, your Atlantic-motherfucking-ocean.
2000		T. Udo Vatican Bloodbath 81: Jesus muthafucken Christ on a fucken pogo stick, boy!
2019		S.M. Jones Lives Laid Away [ebook] ‘You always was Captain Mothafuckin’ America’.
2022		J. Hannaham Didn’t Nobody Give a Shit 35: ‘Don’t even motherfucking think that shit’.