Green’s Dictionary of Slang

(Aus.) an axe; thus swing Douglas, to swing an axe.

1905		Shearer (Sydney) 17 June 6/3: The squatter presents him to ‘Douglas’ (the axe) [AND].
1914		Bulletin (Sydney) 17 Sept. 22/2: With a tommyhawk, or, rather, a half-handled ‘Douglas,’ the gum is chipped off and the sacking catches it as it flies.
1945		Baker Aus. Lang. 78: Kelly and douglas, an axe (from the names of makers), with their derivatives to swing kelly or douglas, to do axework.
1999		G. Seal Lingo 139: An axe was also known [...] as douglas, again based on a (US) brand.