Green’s Dictionary of Slang

1. (N.Z.) an admirable person or object.

1988		McGill Dict. of Kiwi Sl. 94/2: rumty excellent person or thing; contraction of ‘rumti-tum’, an English expansion of ‘rum’, excellent.
2003		McGill Reed Dict. of N.Z. Sl. [as cit. 1988].

2. see rumpty (dooler) n.