An expression of indifference to, or resigned acceptance of, a state of affairs, san fairy ann, also san ferry ann, etc., jocularly represents the French phrase ça ne fait rien, meaning that doesn’t matter.
For example, according to The Guardian (London) of 30th June 2001, the British photographer Jimmy Forsyth (1913-2009) used the phrase in the following context:
His collection of architectural relics […] had been donated to the city’s council-run Discovery Museum, Jimmy explained — “I had a look at it one day and thought, you can’t take it with you when you snuff it” — but he had recently been forced to acknowledge that the museum had “hoyed it out.” “Somewhere down the river,” he said, “all the stuff got dumped. San fairy ann to them. It’s gone with the wind. I don’t cry about it. You can cry all day, and it’s still lost.”
This phrase originated in army use on the Western Front during the First World War; the earliest instance that I have found is from a letter published in The Manchester Guardian (Manchester, Lancashire) on 25th March 1919:
Another phrase I should like to see enshrined in print is on the lines of “Na poo¹”—real French turned into French-English. It is pronounced and spelt (for I took this spelling from the title of a dug-out in all that remained of Givenchy², on the edge of Vimy Ridge) “San Fairy Ann.” The original is “Ca ne fait rien,” and if you mix with the French of the Pas de Calais and the Somme you will hear it a hundred times a day as the equivalent of “N’importe” or the English “That doesn’t matter.” “San Fairy Ann” is now as thoroughly established in the B.E.F.³ patois as “Na poo,” and it has any number of extensions. “San Fairy Ann poor voo,” for instance, is “Mind your own business.” I call it a delightful phrase, in use, spelling, and associations. It deserves to become the battle-cry of some amiable philosophy for taking life easily. Certainly if I am ever lucky enough to put to sea in any craft of my own, blazoned at her bows will be the proud title “San Fairy Ann.”
¹ Also a word that originated in army use on the Western Front during the First World War, napoo represents a poorly apprehended pronunciation of French il n’y en a plus, meaning there is no more of it.
² The Battle of Vimy Ridge took place near the French city of Arras from 9th to 12th April 1917; a fortified knoll near the village of Givenchy-en-Gohelle fell to the Canadian Corps on 12th April.
³ B.E.F.: British Expeditionary Force
On 11th June 1920, The Jedburgh Gazette and Border Courier (Jedburgh, Roxburghshire, Scotland) published a letter in which a certain G. Watson explained that san fairy ann represents ça ne fait rien and sally fairy ann, cela ne fait rien (ça is a contraction of cela):
How Tommy Conforms Words.
The faculty of the soldier of conforming an unfamiliar or unknown word to the sound of another that is familiar is amazing, and I remarked many instances of such during two years on the Western Front. Sitting in the quietude of home, I fondly recall some of these, and record them for the pleasure (or edification!) of the readers of the Gazette. Quite early in the war Tommy learned that if he enquired of the French civilian for ‘Japan,’ the grateful people in response would give him du pain (some bread). The soldier also occasionally referred among his comrades-in-arms to margarine as ‘Maggie Ann.’ The French phrase Cela ne fait rien (that does not matter!) was adopted by us under the guise of ‘Sally Fairy Ann.’ Another rendering was ‘San Fairy Ann’ (for French ca ne fait rien). Feminine names, indeed, were popular, since even the German minenwerfer⁴ was transformed to ‘Minnie Wafer.’ A popular expression was (and is) ‘na poo,’ signifying ‘done, finished. no more, dead, etc.,’ which is a violent cutting down of the French Il n’y en a plus, signifying ‘there is no more of it.’ By ‘toot sweet,’ Tommy represents the French phrase tout de suite, with the same meaning, ‘at once, immediately.’
⁴ The German Minenwerfer, literally mine-launcher, denoted a class of short-range mortars.