Green’s Dictionary of Slang

tear someone up for arse-paper v.

also chew someone up to arse-paper, rip someone up for arse-paper, tear someone up for dunny paper
[SE tear up + arse n. (1)/dunny n.2 + SE paper]

[1910s+] (mainly N.Z.) to scold, to reprimand, to attack and totally overcome in an argument; thus ext. as well, I’ll be torn up for arse-paper!, an excl. of surprise or disbelief.