sergeant-major, n. — Green’s Dictionary of Slang

sergeant-major n.

1. (UK Und.) a burglar’s chisel.

1891

F.W. Carew Autobiog. of a Gipsey 422: The remainder of the outfit comprised [...] a large cold-chisel called the ‘sergeant-major,’ for cutting through metal plates.

2. the crown in the gambling game of ‘Crown and Anchor’ [the NCO’s badge of office].

1919		W.H. Downing Digger Dialects 44: sergeant-major — The crown in ‘Crown and Anchor’.
1924		(con. WWI) A.G. Pretty Gloss. Sl. [...] in the A.I.F. 1921–1924 (rev. t/s) n.p.: sergt. major. The crown in ‘Crown and Anchor.’.

In compounds

sergeant major coffee (n.)

(US) coffee with cream or milk and sugar.

1923

T. Boyd Through Wheat 131: ‘Bring your canteen cups. Sergeant-major coffee.’ [...] ‘Coffee, hot! And milk and sugar in it!’.

sergeant-major’s (tea) (n.) [such beverages are trad. preferred by the NCO]

1. strong sweet tea or tea with rum.

1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 254: Sergeant Major’s Tea, tea with sugar and milk, or a dash of rum, in it.
1930		(con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier.
1948		Partridge Dict. Forces’ Sl. 164: Sergeant-major’s, a Samson-strong, love-sweet brew of tea, popularly supposed to be the perquisite of holders of that rank.
1980		(con. 1930s) Barltrop & Wolveridge Muvver Tongue 21: Sergeant-major’s: extra strong tea.

2. (US) coffee with cream or milk and sugar.

1923

T. Boyd Through Wheat 131: ‘Bring your canteen cups. Sergeant-major coffee.’ [...] ‘Coffee, hot! And milk and sugar in it!’.