Green’s Dictionary of Slang

gaan kak! excl.

[kak v. (1); lit. ‘go shit!’]

(S.Afr.) var. on go to hell! under hell n.

G. Helander Black Rhapsody Translated From The Swedish (2007) 17: ‘Is it you again, you damned bastard? When are you going to pay for what you got last time?’ ‘Excuse, sir, but I ...’ ‘Gaan kak, jou bastard.’.
[US]K.W. Bilby The General 294: ‘Gaan kak in die mielies,’ Nelson muttered, just slightly too quietly for our glaring audience to hear. (‘Go shit in the corn.’).
[SA]P.-D. Uys A Part Hate, a Part Love 52: ‘I won’t!’ Evangelie wailed. ‘These Nazis can gaan kak. gaan kak, gaan kak!’.
P.J.H. Petter-Bowyer Winds of Destruction 230: Damn it Beryl, not only are you pronouncing the words incorrectly, the words Gaan Kak mean go shit yourself.
[SA]Mail and Guardian (Johannesburg) 17 may. [Internet] Gaan kak in jou breke, jou blitsemde Engelse snotneus.