Green’s Dictionary of Slang

barrel of fat n.

(Aus.) a hat.

1905		Duke Tritton’s Letter n.p.: So I threw off my Barrel Of Fat, Dicky Dirt, Rammy Rousers and Daisy Roots, and dived into the Mother and Daughter.
1910		C.E.W. Bean On the Wool Track 163: ‘Look out you don’t lose your old barrel of fat’ means ‘Mind you don’t lose your hat.’ Shirt is probably ‘old lump of dirt,’ and pony ‘Pat Maloney’.
1924		Mail (Adelaide) 16 Feb. 1/4: A hat is sometimes designated ‘barrel of fat,’ or just ‘barrel’.
1935		Advertiser (Adelaide) 12 Jan. 14/8: His barrel of fat blew away and [...] he chased it along the field of wheat.
1950		S.J. Baker in Sun. Herald (Sydney) 8 June 9/5: Detective Doyle has about a dozen rhyming slang words in his list. For example: ‘barrel of fat,’ hat.
1972		Dodson & Saczek Dict. of Cockney Rhy. Sl.
1984		J. Meredith Learn to Talk Old Jack Lang 19: So I threw off my barrel of fat, dicky dirt, rammy rousers and daisy roots, and dived into the mother and daughter.
1999		R. Walton ‘Cockney Jack and the Beanstalk’ 🌐 A little wrinkled heavenly plan with a funny pointed barrel of fat and funny pointed ones and twos and a dirty Quaker oat stepped out into the frog and toad.
2002		Pete’s Aussie Sl. Home Page 🌐 barrel of fat: a hat.