Green’s Dictionary of Slang

absofuckinglutely adv.

[SE absolutely + fucking adj. (4), coined by WWI troops]

very much so indeed, without the slightest doubt; also as an excl. of affirmation.

[UK](con. WWI) N&Q 19 Nov. 415: The soldier’s actual speech [...] was absolutely impregnated with one word which (to use it as a basis for alliteration) the fastidious frown at as ‘filthy’ [...] Words were split up to admit it: ‘absolutely’ became ‘abso-----lutely.’.
[Aus]Baker Aus. Lang. 258: Principal interpolations used are bloody, f—ing, and their euphemisms — e.g. transconti-bloody-nental, abso-f—g-lutely, inde-bloody-pendent.
[US]C. Major Dict. Afro-Amer. Sl.
[US](con. 1969–70) D. Bodey F.N.G. (1988) 225: Abso-fuckin’-lutely. I can remember me and Callmeblack breaking three hundred days.
Union Recorder (Sydney) 4 Nov. 3: We would like to thank every single body who has made this years’ Recorder so absofuckinglutely brilliant.
[US]R.C. Cruz Straight Outta Compton 17: Blowing his gut. Cracking up. Absofuckinglutely.
[UK]N. Barlay Curvy Lovebox 35: Yeah absofokkinlutely, says Getouttamafacesky.
J. Ross Freefall 31: ‘You can absofuckinglutely do this,’ he assured himself for the gazillionth time.