Green’s Dictionary of Slang

doer n.2

[do v.1 (2a)/SE do]

1. [mid-19C] a cheat, one who defrauds another.

2. [20C+] (Aus.) a character, an eccentric, one who never gives up despite any circumstances; often intensified as hard doer under hard adj.

3. [1990s+] (US) a criminal.