Green’s Dictionary of Slang

mucking adv.

a euph. for fucking adv.

1880		Henley & Stevenson Deacon Brodie I tab.III iii: ainslie: What’ll like be my share? moore: You mucking well leave that to me. [Ibid.] IV tab.VII ii: Mucking fine work too, Deacon!
1937		R. Westerby Wide Boys Never Work (1938) 130: Jim [...] told him to mucking well keep quiet unless he wanted the cops after them.
1943		‘Henry Green’ Caught (2001) 63: It’s mucking awful, ain’t it.
1951		D. Stivens Jimmy Brockett 86: A fiver! You tell McGrath I feel mucking well insulted!
1960		A. Sinclair Project 56: Because I’ve mucking well got to eat. Wouldn’t we all lie around like prize pussies if we hadn’t mucking well got to eat?
1976		‘In The Melting Pot’ in P. Ashton et al. Our Lives (1982) 168: You talk too mucking fuch.
2007		F. Leiber Green Millennium 30: You know mucking well I can stand anything except when you start bullying people.