1976 P. Callow vi. 42 ‘When's your case come up?’ David said. ‘Fuck knows’.
1988 G. Patterson iii. ix. 245 I know what youse're thinking: ‘he must be mad’. Well, if that was mad, then fuck knows what youse'll say when youse see the next knockdown bargain.
2001 C. Glazebrook 302 Tell spaceboy to turn the volume down. I can't get through to him, fuck knows what he's on.