(Aus./N.Z.) berserk; in weakened form, temporarily out of control.
|Hang On a Minute, Mate (1963) 163: When he’s got a few in he goes berko.|
|Dict. of Kiwi Sl. 14/1: berko berserk, though not really; to go berko is to be temporarily angry and out of control.|
|Aus. / NZ Jrnl Sociology XXVII n.p.: I just went absolutely berko on her.|
|Reed Dict. of N.Z. Sl. 20: berkers/berko Somebody considered excessively silly or angry, crazy or out of control [...] usually in the phrase ‘to go berko’. ANZ mid C20.|