your mother!, excl. — Green’s Dictionary of Slang

your mother! excl.

also your maw! your mom! your momma!

[euph. for go fuck your mother! under fuck v.]

(orig. US, mainly teen) a rejoinder to an insult, implying that whatever that insult is, it applies most to the speaker’s own mother; see also yo’ mama! excl.

1953		F. Paley Rumble on the Docks (1955) 86: ‘Your mother!’ Pooch murmured.
1964		P. Marshall ‘Some Get Wasted’ in Clarke Harlem, USA (1971) 353: They [...] sounded each other’s mother: ‘Yoa mother, man.’.
1972		C. Fuller Jr ‘Love Song for Wing’ in King Black Short Story Anthol. (1972) 145: ‘Your motha!’ she yelled.
1985		T.R. Houser Central Sl. 60: your momma A curse which is an counter to a slur.
1993		A. Rodriguez Spidertown (1994) 110: You know how they say, never say yuh motha to a Puerto Rican, how if you do, he’ll kill you? Well, not me.
1997		N. Barlay Curvy Lovebox 45: They [...] start chantin’ the same thing at each other. — Yer mum yer mum yer mum.
1999		Eble Campus Sl. Apr. 8: your mom – insulting retort.
2007		T. Dorsey Hurricane Punch 8: Now he’s yelling something about your mother.
2020		G. Armstrong Young Team 11: ‘Aye so yi huv, Broonie!’ ‘Yir fuckin maw’.

In exclamations

your mother’s cunt! (also your mother’s arse! ...box! ...twat!) [cunt n. (1)/box n.¹ (1a)/twat n. (1)]

a derisive, dismissive excl.

1952		J. Jones From Here to Eternity (1998) 38: ‘Your face,’ Leva said. ‘Your mother’s box,’ Milt said.
1975		J. McClure Snake 38: ‘Your mother’s arse!’ flared Zondi in Zulu.
1975		E. Torres Carlito’s Way 117: Yer mudder’s cunt, I thought. [Ibid.] 140: Mother’s twat, just when I gotta concentrate on my case.
1981		G. Young Slow Boats to China (1983) 95: Around me, gap-toothed mouths reeking of beer scream ‘Your mother’s c---!’.
2011		Mail and Guardian (Johannesburg) 6 May 🌐 One man even shouted [...] that he would teach me a lesson because I’m like a man. I shouted back: ‘Your mother’s pussy you will teach me a lesson’.