Green’s Dictionary of Slang

motherfucking adj.

also m-fugging, mothahfuggin, motherfugging, muthafucken, muthafuckin, sisterfucking
[motherfucker n.]
(orig. US)

1. a general intensifier.

[US]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].
[US]‘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‘.
[US]M. Levin Old Bunch (1946) 122: You mother-f– little runt.
[US](con. 1944) N. Mailer Naked and Dead 10: Of all the mother-fugging luck.
[US]Kerouac letter 12 Oct. in Charters I (1995) 381: I start West in the rain [...] I go 3,000 motherfucking miles.
[US]R. Gover One Hundred Dollar Misunderstanding 21: Twenty berries an you alla roun the mothahfuggin worl’.
[US](con. 1953–7) L. Yablonsky Violent Gang (1967) 82: Where are those mother-fuckin’ punks?
[US]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.
[US]R. Price Ladies’ Man (1985) 25: I have big motherfucking strong hands.
[US]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!
[US]B. Hamper Rivethead (1992) 94: I was one blazin’ tomahawk of m-fuggin’ eel snot.
[US]Dr Dre ‘187’ 🎵 Niggas keep your hands on your motherfuckin’ shit.
[UK]Guardian Guide 17–23 July 27: Nor is he likely to encourage us to ‘make some muthafuckin’ noise’.
[US]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.
[UK]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!
[UK]L. Theroux Call of the Weird (2006) 187: I done told you three motherfuckin’ times, no touching.
[Aus]B. Matthews Intractable [ebook] In that moment he was every motherfucking screw that ever bashed me.
[US]M. McBride Swollen Red Sun 130: Listen here, you cornholin’, sister-fuckin’..
[US]N. Walker Cherry 190: ‘Is that motherfucking Lieutenant Nathan?’.
[UK]‘Aidan Truhen’ Seven Demons 282: [A] cane with a rat skull on the top which I am motherfucking twirling.

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

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