Green’s Dictionary of Slang

as past participle, used as an intensified version of damn v. (2); often as fucked if...

1948		N. Mailer Naked and Dead 157: Ah’m fugged if Ah’ll wait for any ole deer.
1960		C. MacInnes Mr Love and Justice 33: Well, I’ll be f---d!
1985		‘Thommo’ Dict. Aus. Swearing & Sex Sayings 51: FUCKED IF I KNOW — The reason used when not knowing the correct answer to a question. Or to relieve one of the responsibility of answering a question.
1987		(con. c.1967) J. Ferrandino Firefight 34: ‘Where the fuck are we?’ he said. ‘Fucked if I know,’ Malone answered.
1991		L. Bing Do or Die (1992) 5: Some of the kids were sitting there [...] fucked if this place was going to break them down.
1998		R.G. Barrett Mud Crab Boogie (2013) [ebook] ‘Fucked if I know what I’m gonna do’.
1999		Guardian Guide 26 June–2 July 12: I’m fucked if I know.
2000		N. Griffiths Grits 45: So anyway, am fucked if am stayin sober tuhnight.
2000		T. Udo Vatican Bloodbath 17: Ah’m fucked if I know whit tae dae.
2000		R.G. Barrett Leaving Bondi (2013) [ebook] [F]ucked if I know what you’re talking about anyway.