A dapto briefcase refers to cask wine and wine bladders. Another common slang names is "goon bag". Dapto is a suburb of Wollongong in NSW.
Look. A dapto briefcase for only $5.
by Dapto Briefcase April 18, 2006
Origin: Many many moons ago when the rainbow serpent was lying dormant Cecil would say he's off to work and he would tell the passer bys that the box of wine he was holding was his Dapto Briefcase and he was working hard for the government.
by PunX0r April 10, 2007