meaning and origin of the phrase ‘not to know — from a bar of soap’

The colloquial phrase not to know — from a bar of soap means to be completely unacquainted with — (cf. also no to know — from Shinola).

In both:
– the Oxford English Dictionary (2nd edition, 1989)
and
A Dictionary of Australian Colloquialisms (Sydney University Press in association with Oxford University Press Australia, 1990), by Gerald Alfred Wilkes (born 1927), professor of Australian literature at the University of Sydney,
the earliest quotation is from the following cartoon by Stan Cross (Stanley George Cross – 1888-1977), published in Smith’s Weekly (Sydney, New South Wales) of Saturday 26th November 1938—this cartoon depicts two down-and-out men in a public park; one, sitting on a bench, says to the other, standing beside him, with a bundle under his arm:

I don’t know you from a bar of soap

The other replies:

No – I suppose we’re both strangers to you

The caption is:

SAYS HE SCORNFULLY: “I don’t know you from a bar of soap!”

'not to know from a bar of soap' - Smith's Weekly (Sydney, New South Wales) - 26 November 1938

 

However, the earliest uses of not to know — from a bar of soap that I have found date from the late 19th century, and are from U.S. publications—except two, which are from Australian newspapers.

The earliest occurrence punningly contrasts two acceptations of the noun bar; it is from The Chicago Daily Tribune (Chicago, Illinois) of Wednesday 30th May 1877—itself quoting the St. Louis Globe-Democrat1 about “the Soldene2 troup”:

The ‘prima donna’ does not know a bar of music from a bar of soap; the chief actor would not be allowed to play supernumerary in a dumb show […].”

1 I have searched in vain for the original article in the St. Louis Globe-Democrat (St. Louis, Missouri).
2 Emily Soldene (1838-1912) was an English comic-opera singer, actress-manageress, novelist and journalist.

The very same punning use of bar occurs in the St. Louis Post-Dispatch (St. Louis, Missouri) of Saturday 6th January 1883, about the last-minute cancellation of a concert by the Swedish opera singer Christina Nilsson (1843-1921):

The young men of fashion who—to use a vulgar expression—don’t know a symphony from a sardine, and could not tell a bar of music from a bar of soap, but who in deference to the dictates of fashion had bought tickets for to-night—they are not wholly unhappy and do not mourn as those who refuse to be comforted.

The phrase not to know, or not to be able to tell, a bar of music from a bar of soap has been regularly used since then.

The second-earliest occurrence of not to know — from a bar of soap that I have found is from an Australian publication, The Freeman’s Journal (Sydney, New South Wales) of Saturday 11th May 1878—not to know B from a bar of soap refers to the letter B and means to be entirely illiterate—cf. earlier synonymous phrases such as to know a B from a bull’s foot and not to know a B from a battledore:

TOWN TALK.

[…]
Bret Hart gives the “Heathen Chinese” credit for being an adept in “ways that are dark and tricks that are vain,” and Mr. Cameron, the member for West Sydney, would give the meek Ah Sin something more—a very wide berth. It seems that the “tribune of the people” is not by any means inclined to see New South Wales made a home or refuge for the swarming sons of the Flowery Land, and for once I cordially agree him. I don’t see much to love in Sun Kum Along myself—in fact, I’d rather see him stay at home. He is not handsome, to begin with, and although boasting a civilization which reaches so far back as to be lost in the mists of time, yet I doubt whether he has learnt the use of soap and water to any considerable extent, which shows that his civilization is of a very poor kind, notwithstanding its antiquity. I have heard some very estimable people, generally of the missionary-parson type, speak with the greatest veneration of the literature and arts of the Chinese at a period when we Europeans didn’t know B from a bar of soap; but, for all that, I don’t see the evidence of culture and refinement in a people whose dinner service is limited to two pot-sticks, with which they manage to sling rice out of sight at a pace that is truly bewildering. “John” may be an inimitable cabbage grower, a tolerable cook, and an unequalled laundress—he may be frugal to a degree, meek, industrious, and uncomplaining (that is, in our language), but still it is hard for a Britisher that he should be regarded as “a man and a brother,” and treated as one having equal rights.

A variant of the phrase occurs at the beginning of an unsigned and untitled short story in seven chapters, published in The Chicago Daily Tribune (Chicago, Illinois) of Sunday 5th October 1879:

There was an old farmer out in a small Iowan settlement who had one daughter, and she was probably the homeliest woman that ever wore a No. 11 shoe. She was red-haired, cross-eyed, and freckled, with as much figure as a pine-slab, and feet of such generous proportions that she seemed to have been bent in two at her ankles like a foot-rule. She could not tell an air by Verdi from a bar of castile soap, and spelled “kiss” with a “c” and a “z.” Art had done as little as nature to beautify her, and that was saying volumes,—nay, whole encyclopoædias.

The following humoristic text is from The Irish-American (New York City, N.Y.) of Saturday 21st October 1882:

RUNNING FOR OFFICE.
The Sad Experience of Poor Boggs.

Boggs was as peaceable a man as ever lived. He was sober, honest and respected. He had never beaten his wife; never taken interest in a dog fight; had never been known to pawn anybody else’s watch, and never had attempted to steal a saw-mill. Bogg’s character was above reproach. He was a shining light in society. All his fellow-citizens looked up to and honored him. He was extremely popular among the ladies. But a change came—a fearful, direful change. In an evil hour Bogg’s accepted the nomination for School Director—without salary.
Alas! Poor Boggs!
Little did he understand the deceit and treachery of the wicked world. His eyes were soon opened, however, for in less than a week after he was nominated, the opposition had fully established the following damaging charges against aim [misprint for ‘him’]:—
1.—That he was a free lover.
2.—That he was a secret emissary of the Pope of Rome.
3.—That he had broken his mother-in-law’s jaw with an iron boot-jack.
4.—That, if elected, he would make love to every school “marm” in the Department.
5.—That he had served a term in the State Prison for horse-stealing.
6.—That he got his washing done at a Chinese laundry.
7.—That because he found a button off his shirt he tied his wife to the bed-post and mashed in three of her ribs with a stove poker.
8.—That his chief Sunday amusements were picnics and pedro3.
9.—That he didn’t know a di-junctive conjunction from a bar of soap or a bar-sinister.
10.—That he wasn’t fit for the place anyhow.

3 The noun pedro denotes a variation of the game Pedro Sancho in which the sancho, or nine of trumps, does not count – The noun Pedro Sancho denotes a card game like all fours or cinch, in which the nine and five of trumps have their face value and the ten of trumps wins the game.

Published in the Meriden Report (Meriden, Kansas) of Saturday 14th May 1887, the following portrait of “a bum” is based on the grammatical pattern I have heard him talk — when he did’nt know — from —:

This bifurcated animal is a very talkative fellow. He would be a fortune to any stockman as a wind producer. He is very particular what he talks about and generaly [sic] chooses a subject of which he knows as little as the average Greenbacker does of National finance. I have heard him talk politics when he did not know the meaning of “Suffrage,” and at the coming election sold his vote to the highest bidder; and the man that bought it belonged to the same crowd.
I have heard him talk finance when he did’nt know a greenback from a Mexican dollar and had none of either. I have heard him talk religion when he did’nt know the ten commandnents [sic] from the Presidents last message, or theology from – well from the Democratic platform. I have heard him talk astronomy when he did’nt know a comet from a cow. I have heard him talk medicine when he did’nt know a blue pill from a bar of soap and he had more to say on all these subjects than the man that knew all about them.

On Wednesday 29th June 1887, The Potter Enterprise (Coudersport, Pennsylvania) published a short epistolary text, in which Jim, of Austin, Pennsylvania, writes to Blanche, of Hebron, Pennsylvania:

You may have me, if you want to, for, to tell the truth, my love for the rest of the girls is no more to be compared to my love for you than a tumble-bug is to a mastodon.
Though I do not know you from a bar of soap.

The second-earliest Australian use of not to know — from a bar of soap that I have found is from The Darling Downs Gazette (Toowoomba, Queensland) Saturday 23rd February 1889:

Those Bricks.—At a meeting of the Waterworks Committee held at the Town Hall on Wednesday last, the bricks used in the new well were flung about pretty well, figuratively speaking. […] Alderman Stirling alleged he saw some of the very poorest bricks put in that well. Alderman Garget declared he had been brickmaking or among bricks all his life, whereas Alderman Stirling didn’t know a brick from a bar of soap, or something to that effect. Being a committee meeting, we did not attend and only go by hearsay.