Green’s Dictionary of Slang

rabbit-o n.

also rabbie, rabbit-oh
[the cry, but note Aus. -o sfx (3); thus The Rabbit-Os, derog. nickname for the South Sydney Rugby Club, whose fortunes suffered so much in the 1930s Depression that its officials were reduced to raffling and selling rabbits]

[20C+] (Aus.) an itinerant seller of rabbits as food; also attrib.