Green’s Dictionary of Slang

1. a penny [refers to the copper coins struck in 19C by Boulton & Watt at their works in Birmingham].

1914

E. Wittmann ‘Clipped Words’ in DN IV:ii 121: Brum, from Brummagem. 1. A counterfeit coin. [...] 3. Copper money struck by Boulton and Watt at their works at Soho, Birmingham (1787).

2. a counterfeit coin.

1789		G. Parker Life’s Painter 133: So nobles and gents, lug your counterfeits out / I’ll take brums or cut ones, and thank you to boot.
1833		‘The Masqueraders’ in Corinthian in Spedding & Watt (eds) Bawdy Songbooks (2011) IV 42: Now nobles and gents, Ing your counterfeits out,/ I’ll take brums or cut ones, and thank you to boot.
1860		Hotten Dict. of Modern Sl. etc. (2nd edn) 105: Brums counterfeit coins. Nearly obsolete. Corruption of Brummagem (Bromwicham,) the ancient name of Birmingham, the great emporium for plated goods and imitation jewellery.
1864, 1867, 1870		Hotten Sl. Dict.
1914		see sense 1.

3. something inferior.

1883

DT 9 July 3 2: One [earring] might be gold, and the other a Brum, though exactly alike [F&H].

4. (Aus./US) cheap goods, esp. showy clothes.

1915		C.J. Dennis ‘The Intro’ in Songs of a Sentimental Bloke 19: I seen ’er in the markit first uv all, / Inspectin’ brums at Steeny Isaac’s stall.
1926		J. Black You Can’t Win 163: I’m dynamite with them old brums in the cribs.
1963		R. McGregor-Hastie Compleat Migrant 105: Brums: best clothes or cheap jewellery.