Green’s Dictionary of Slang

cha n.1

also chah, chai, char, chi
[Mandarin ch’a, tea]

tea.

[Ind]Delhi Sketch Bk 1 Aug. 95/1: [from London Dly News] Cha is popular amongst the men and officers of the fleet [...] to find that the Tars have taken to Cha does not, we think, argue well for their jollity.
[UK]P. MacGill The Great Push 165: ‘There’ll be some char (tea) in a minute,’ said Bill.
[UK]A.G. Empey Over the Top ‘Tommy’s Dict. of the Trenches’ 286: Char. A black poisonous brew which Tommy calls tea.
[UK]‘J.H. Ross’ Mint (1955) 118: ‘Get yourself a cha,’ he insisted gently.
[UK](con. WWI) Fraser & Gibbons Soldier and Sailor Words 51: Char: (Hind. — Chhah). Tea. (Old Army).
[UK](con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier.
[US]W.A. Gape Half a Million Tramps 27: Blimey, can’t a respectable lady come in for a cup of ‘char’ without being disturbed by the police?
[UK] ‘Frightfully G.H.Q.’ in M. Page Kiss Me Goodnight, Sgt.-Major (1973) 111: We’ve even drunk cups of what NAAFI calls ‘chai’.
[Aus]Sydney Morn. Herald 11 Dec. 7/1: ‘Chai’ or ‘shay’ for tea has wide currency.
[UK]R. Llewellyn None But the Lonely Heart 283: Pot of chah.
[Aus]Smith’s Wkly (Sydney) 27 May 14/3: Two other importations, ‘browned-off’ (fed up) and ‘chi’ (tea) have been adopted [by Aus. troops].
[UK]J. Maclaren-Ross Swag, the Spy and the Soldier in Lehmann Penguin New Writing No. 26 31: I’m for a cup o’ char.
[NZ](con. 1940s) G. Slatter Gun in My Hand 92: The Kiwis in the dugout are brewin up the chai.
[UK]C. MacInnes Absolute Beginners 24: Dad knocked on the door with two cups of char.
[UK]K. Amis letter 10 Mar. in Leader (2000) 620: Their place is in an Old Kent Road cabmen’s shelter, taking scoff and char.
[Aus]Aus. Women’s Wkly 4 Sept. 2/3: More their cup of tea (or cuppa cha) are this year’s designs.
[UK](con. WWII) B. Aldiss Soldier Erect 34: Tea-vendors [...] uttering that endless melancholy cry, ‘Chaeeeeee wallow’.
[UK]P. Theroux Family Arsenal 140: No more bloody char.
[UK]M. Amis London Fields 302: You could have treated me to ‘a wad and char’.
[Aus]J. Byrell Lairs, Urgers & Coat-Tuggers 52: [T]he ladies weren’t just there to serve the date scones and cha.
[UK]Guardian 9 Oct. 26: A nice cup of char, Mr Guyler.
[UK]Guardian 2 Aug. 11: If you need to find out which countries [...] prefer a cup of cha.
[Scot]T. Black Artefacts of the Dead [ebook] He placed the cup in front of her. ‘Nice cup of char, eh’.
[UK]J. Meades Empty Wigs (t/s) 655: ‘What you needs is a nice strong cup of cha and a wad’.

In compounds

char wallah (n.) (also lemonade-wallah, pop-wallah) [wallah n. (1); note Hind char-wallah, a tea-seller]

a teetotaller.

[UK]N&Q 12 Ser. IX 424: Lemonade Wallah/Pop-Wallah. Teetotaller.
[UK](con. WWI) F. Richards Old Soldiers Never Die (1964) 119: If a teetotaller he was known as a ‘char wallah’, ‘bun-puncher’ or ‘wad-shifter.’.