Green’s Dictionary of Slang

1. healthy, esp. free of venereal disease.

1575-83		‘Bashe Libel’ in May & Bryson Verse Libel 79: Ther was no harlott to be found, / Yea, wear she sore or wear she sound. / But he durst broach her barrell-low.
c.1642		T. Killigrew Parson’s Wedding (1664) II vii: Why, I am sure ’tis a provident and safe way; a man may always be provided and sound.
a.1661		‘A Free Parliament Letany’ Rump Poems and Songs (1662) II 187: From Harry Martins Whore, that was neither Sound nor Pretty.
1673		‘Letter from a Missionary Bawd’ in Carpenter Verse in English from Tudor & Stuart Eng. (2003) 427: Although no virgins, I’ll assure them [i.e. a group of prostitutes] sound.
c.1695		‘The Beggar’s Delight’ in Farmer Merry Songs and Ballads (1897) IV 57: She’s sound, she’s sound, she’s sound, / And free from the Plague and Pox of the Town.
c.1709		‘The Female Scuffle’ in Farmer Merry Songs and Ballads (1897) IV 213: The Bauds and Buttocks that liv’d there around, / Came all to the Case, both Pockey and Sound.
1764		Foote Mayor of Garrat in Works (1799) I 162: As to your scurvys and gouts, [...] coughs and catarrhs, tar-water and turpentine will make you as sound as a roach.
1913		J. London Valley of the Moon (1914) 195: As Saxon’s strength came back to her (and when Doctor Hentley had privily assured Billy that she was sound as a dollar), she herself took up the matter.
1942		W.R. Burnett Quick Brown Fox 32: I’m sixty years old and sound as a dollar.

2. excellent, first-rate, totally satisfactory, admirable, dependable.

[c.1614		Beaumont & Fletcher Bonduca IV i: pet.: Are thy brains perfect? jun.: Sound as bells].
c.1800		‘Sandman Joe’ No. 23 Papers of Francis Place (1819) n.p.: My dearest Joe I know you / As sound a dog as ever piss’d.
1824		‘Geoffrey Crayon’ Tales of A Traveller (1850) 146: A hearty old blade that. Sound as pitch. Old Turpentine! as we used to call him.
1833		‘Sandman Joe’ Lummy Chaunter 82: O then they kissed, and then shook fist, / My dearest Joey, don’t I know you? / Why you’re as sound a dog as ever p---d.
1879		C.J. Kickham Knocknagow 136: ‘Sound man, Mr Hugh!’ he added, as Hugh presented him with two half-crowns.
1908		‘Doss Chiderdoss’ ‘Penny Numbers’ Sporting Times 11 July 1/3: I’d no money to treat her, so I had to seek / Some kind gent whose finances were sounder.
1914		C. Holme Lonely Plough (1931) 126: Hamer became known as ‘sound,’ ‘useful,’ ‘a man at a pinch’.
1958		A. Sillitoe Sat. Night and Sun. Morning 7: Loudmouth’s tactics were skilful and sound, he had to admit that.
1980		Séamus de Faoite More we are Together n.p.: The faces that tiered all the way to the roof at the back came alive in cheers and shouting when the pair came in sight. ‘Sound man, Joe Jack!’ [BS].
1986		‘Old Zebra Dun’ in G. Logsdon Whorehouse Bells Were Ringing (1995) 82: On a burro sat a stranger, and he didn’t look too ‘sound,’ / For he was so durn long legged that his big feet touched the ground.
1993		I. Welsh Trainspotting 84: Dinnae git us wrong like; ah thoat the cunt wis fuckin sound.
2000		N. Griffiths Grits 69: Ee’s a sound twat (most-a a time; a fuckin shite-arse twat, iffa trewth be fuckin telt).
2005		P. Howard Curious Incident of the Dog in the Nightdress 31: He is actually gay, roysh, but he’s still sound.
2009		L. McIlvanney All the Colours 18: He might think I’m sound [...] But does he think I’m any good?
2017		hubpages.com ‘Roadman Slang’ 4 Jun. 🌐 Sound - very similar to ‘safe’ but is slightly more positive, e.g. ‘John is a sound guy’. Mainly used in Northern-England, but increasingly heard in East London.
2019		A. Killilea Boyo-wulf at https://boyowulf.home.blog 24 Mar. 🌐 Sound deeds will earn you respect with anyone.

3. dependable, trustworthy, of sober judgement (in the view of the speaker).

1865		A.D. Richardson Secret Service 34: The New Yorker was swift to explain that he was very ‘sound,’ favoring no compromise which would not give the slave holders all they asked for [DA].
1885		Bulletin (Sydney) 30 May 14/4: Verily, the wise man was sound on the goose when he said: ‘He that taketh a woman by her word and an eel by its tail may be considered to hold tightly on to nothing.’.
1894		Truth (Sydney) 4 Feb. 4/8: Mr Hosea Bigelow was pretty sound on the goose when he said [etc.].
1986		D. Marcus A Land Not Theirs 158: Good boy. Sound man. Honour thy father and thy mother – isn’t that right?
1996		P. Howard The Joy (2015) [ebook] Derek was sound. We were never what you’d call good mates, but we were as friendly as two junkies can be.
2012		(con. 1980s) I. Welsh Skagboys 315: —He’ll be awright, Tommy said hopefully. —Calum’s sound.
2014		Observer 13 Apr. 17/4: You gotta be very sound.
2015		L. McInerney Glorious Heresies 220: ‘They’re all sound,’ he said, ‘honest to fuck’.
2020		G. Armstrong Young Team 12: ‘Fancy jumpin in the shop fur us, eld son [...] eh?’ A say, actin pure sound.

4. safe.

2001

K. Sampson Outlaws (ms.) 72: Go on your tod. You’ll be sound.