The phrase the clean potato means: the very, the real, or the proper person or thing.
This phrase seems to have originated in Scottish English, since all the earliest occurrences of the clean potato that I have found are from Scottish publications, in particular from a collection of Scottish proverbs—cf., below, quotation 3.
However, the author of Tick on Scientific Principles, published in Blackwood’s Edinburgh Magazine (Edinburgh, Midlothian, Scotland) of November 1838, hinted at an Irish-English origin, since he specified, when translating the phrase the man comme il faut * as the Clean Potato, that he did so “in the language of Hibernian Curran”.
(* The French phrase comme il faut (literally as it must) means in keeping with etiquette or social standards.)
In any case, contrary to what the Oxford English Dictionary (OED – online edition, March 2022) states, the phrase the clean potato did not originate in Australian English.
The OED erroneously states that the phrase originated in Australian English because the earliest occurrence that this dictionary quotes is from Adventures in Australia, in 1852 and 1853 (London: Richard Bentley, 1853), by the Rev. Henry Berkeley Jones—however, here, the expression is a clean potato, not the clean potato:
One awkwardness felt by a “new chum” is, that you do not know whether the man who addresses you is or has been a convict; and it is not very complimentary to ask one who speaks to you, “Are you,” in the idiomatic phraseology of the bush, “a clean potato?” If he is not a convict , he must think he has a convict’s look; if he is, why recall to him—why reproach him—with that which he is trying to make reparation to society for?
Unfortunately for the OED, in Henry Berkeley Jones’s text, the expression clean potato does not mean the very, the real, or the proper person, but designates a free man in Australian convict slang—as explained by Sidney John Baker (1912-1976) in The Australian Language (Sydney and London: Angus and Robertson Ltd., 1945), page 44.
In fact, the earliest occurrence that I have found of the phrase the clean potato in an Australian publication is from the reprint, in The Launceston Advertiser (Launceston, Tasmania) of Wednesday 21st December 1831, of a paragraph from The Loyal Reformers’ Gazette (Edinburgh, Midlothian, Scotland) of Saturday 7th May 1831—cf., below, quotation 2.
The earliest occurrences of the phrase the clean potato that I have found are as follows, in chronological order:
1-: From The Edinburgh Literary Journal; Or, Weekly Register of Criticism and Belles Lettres (Edinburgh, Midlothian, Scotland) of Saturday 12th June 1830:
REMARKS ON GAMBLING, WITH SOME ALLUSIONS TO A DIRTY STORY.
By Lieut. ——, late of the Royal Irish Dragoons.
I don’t know how it is, but there’s a world of difference betwixt our own little island and the continent. […] Now, all over the continent, […] there comes to be a regular class who live at or by the gaming table, and it shoots so many polypus-like fibres into the great mass of society, that you cannot tell where the honest set leave off, and the rogues begin. But, if I might venture on stating my own belief, I would say, that it is more difficult to meet on the continent with one who is quite and away the clean potato, but that it’s seldom you’ll meet with such devil’s own pigeons as here at home.
2-: From The Loyal Reformers’ Gazette (Edinburgh, Midlothian, Scotland) of Saturday 7th May 1831:
Henry Hunt.—We regret exceedingly that this man has been returned again for Preston.—He is not the clean potatoe. After the late exhibition he made in Parliament, we can no longer place any dependence on him. We are satisfied that Wellington and Peel understand him well. Would that party have put themselves to the trouble and expense of getting his crooked speech printed and circulated gratis throughout the country in the way they did, unless there was something under it?—Hunt must be watched narrowly.
3-: From the Miscellaneous section of Scottish proverbs, collected and arranged by Andrew Henderson (Edinburgh: Oliver & Boyd, 1832):
He is like the Kilkenny cat—he has left naething behind him but his tail.
He is a causey saint and a house deil.
He’s no steel in the back sprent.
He’s no the clean potatoe.
He’s no sae daft as he lets on.
4-: From Noctes Newhavenæ. Electioneering dialogue, published in A Collection of political effusions which appeared during the late election (Leith (Scotland): Printed by R. Allardice, 1834):
Tam. Weel, Philip, did ye no see the letter about this new Election? […] its frae [a] Vriter chiel ca’d Black Mercury, wha […] after a’ the favours got frae Mr. Murray, has gane o’er to the Aitchison side, to prevent our freen, the Lord Advocat to be, frae being Member in Parlimint.
Philip. O, the black loon! to turn frae oor side, and join the Tories. What base ingratitude to puir Mr. Murray—honest man! […]
Tam. A-weel, a-weel, Philip, that’s no the warst o’t.
Philip. What! is there ony mair o’ them turn’d traitors, Tam?
Tam. Ou, aye, anither ane, Philip! Its that bodie, Sam, the wee Vriter they ca’ Grippy. He’s no the clean potatoe either. For a’ past kindness he’s aff to the yellow party, and is noo hand and gluv wi’ Black Mercury, wurking against puir Mr. Murray!
5-: From Portrait of a Tory Radical, published in The Manchester Times. And Lancashire and Cheshire Examiner (Manchester, Lancashire, England) of Saturday 26th August 1837—reprinted from “a Manchester newspaper”:
“As the tory-radical’s policy is all or nothing, he has an intense hatred of the philosophical and practical radical. Does the latter propose to take a part of his rights without abandoning his claims to all, he is a truckler to expediency. Does he ask for the ballot, without at the same time asking for an extension of the suffrage, he is a vile aristocrat. Does he ask for the ballot and household suffrage, he is an enemy to the working classes, because they are entitled to universal suffrage. Does he, like Roebuck, go the whole hog of democracy, but deny that the poor law amendment act is all bad, he is a base whig. Does he venture to say that Cobbett was inconsistent, or that Oastler is violent, or that Stephens is not quite the clean potatoe, he is a base and vile whig. Does he say that their vapouring organ writes nonsense, he is a base, vile, and bloody whig. Does he say it is folly to devote all the energies of body and soul to destroy the bastardy clause in the poor law act, he is a base, vile, bloody, and damnable whig!”
The phrase the clean potato may be an extended form of the synonymous phrase the potato, which occurs, for example, in the following two extracts:
1-: From Noctes Ambrosianæ. No. I, published in Blackwood’s Edinburgh Magazine (Edinburgh, Midlothian, Scotland) of March 1822:
Editor. The Bishop’s first two volumes are not quite the potato. I hope the others are better.
Odoherty. Who cares? I shall never read them.
2-: From Noctes Ambrosianæ. No. III, published in Blackwood’s Edinburgh Magazine (Edinburgh, Midlothian, Scotland) of May 1822:
Tickler. I hope you’ll excuse my gaiters, North; I had not the least idea you were to sport a regular blow-out to-day. I looked into the other room, and saw such a smash of covers—And you in your silk stockings too!—I suppose you’ve been sporting your ankles with the Commissioner.
North. Not I; but I expect several strangers to dinner, and an Editor is nothing without black breeches, you know—But you need not say a word about your dress. Upon my honour, that’s a most natty surtout—and your spatterdashes, why they are quite the potato. For a contributor you are well enough—and, after all, there’s no ladies in the party.