The colloquial phrase down the Swanee means completely lost or wasted—synonymous phrases: down the pan – down the toilet – down the tube(s) – down the plughole – down the drain – down the gurgler.

Although down the Swanee is a British-English phrase, it seems to allude to a U.S. minstrel song, Old Folks at Home, also known as Swanee River, composed in 1851 by Stephen Foster (1826-1864).

This song was inspired by the Suwannee River, which flows from the Okefenokee Swamp in southern Georgia to the Gulf of Mexico in Florida.

This is the beginning of the song—from Old Folks at Home, Ethiopian Melody, as sung by Christy’s Minstrels. Written and composed by E. P. Christy* (New York: Firth, Pond & Co., 1851):

Way down upon de Swanee ribber,
Far, far away,
Dere’s wha my heart is turning ebber,
Dere’s wha de old folks stay.

All up and down de whole creation,
Sadly I roam,
Still longing for de old plantation,
And for de old folks at home.

Chorus.
All de world am sad and dreary,
Ebry where I roam,
Oh! darkeys how my heart grows weary,
Far from de old folks at home.

(* The U.S. composer, singer, actor and stage producer Edwin Pearce Christy (1815-1862) was the founder of the blackface minstrel group Christy’s Minstrels. Stephen Foster sold him the right to call himself the composer of Old Folks at Home for $5.)

This song was hugely popular in Britain from the late 19^th to the early 20^th centuries. The earliest mention that I have found is from the following advertisement, published in The Standard (London, England) of Thursday 1^st September 1887:

MDLLE NIKITA will Sing the “Jewel Song” from “Faust” (Gounod) and “Down the Swanee river” (Foster), TO-NIGHT, at HER MAJESTY’S THEATRE.

This song became also known as Way down the Swanee River, Way down upon de Swanee Riber, Away down the Swanee River, and variants. For example:

1: The following is from the Totnes Times and Devon News (Totnes, Devon, England) of Saturday 29^th September 1888:

The members and friends of the Barnstaple Conservative Association were on Monday and Tuesday evenings afforded a most enjoyable musical treat […]. On Monday […], the first song of the evening was given by Mr H. Lovell, “Way down the Swanee River.”

2: The following is from Irish Society (Dublin, County Dublin, Ireland) of Saturday 22^nd March 1890:

Clontarf Choral Society.—[…] Miss Alice Healey was found to acquit herself with signal and characteristic distinction. […] The pathetic plantation melody, “Way down upon de Swanee Riber,” received from her a consummately perfect interpretation.

By the early 20^th century, the song had become so popular in Britain that the British novelist, playwright, essayist and historian John Hay Beith (1876-1952) used down the Swanee River as a synonym of old folks at home in Half a Sovereign. An Improbable Romance, written under the pen name of Ian Hay—as published in The Graphic (London, England) of Saturday 19^th June 1926 (George Bumpstead is “an explorer, big game hunter and oaf of the first water”; Mr. Podmore “is enthusiastic over such things as Morris dancing and folk-lore”; Lila Chatterton is a “modernist” youngster):

“What in hell is a Morris dance?” enquired George Bumpstead.
[…]
“You will soon know, Georgie,” she [= Lila] replied. “Podmore will dress you up in a smock-frock, and a top-hat brushed the wrong way, with chiffon round it; and they’ll tie leggings round your legs with bells on, and give you two silly little sticks to crack together.”
“My God, what for?” enquired George Bumpstead, simply.
“To cultivate the old folk spirit.”
“What old folk?”
“I don’t know, dear. But I fancy it’s the old folks at home—down the Swanee River, and so on.”

The following from The Western Times (Exeter, Devon, England) of Friday 16^th June 1933 also bears witness to the popularity of the song:

Torrington Town Council on Tuesday received a complaint from the Taw and Torridge Fishery Board of alleged pollution of the River Torridge […].
[…]
Alderman G. M. Doe said there was one thing very funny which seemed to have been omitted from the letter. He saw it was reported that at the Taw and Torridge Conservators’ meeting it was stated that bedsteads, gramophones, and umbrellas were going down the river. He thought they should know whether they were wood or iron bedsteads, because the effect on the fish would depend whether they floated down or sank. Also it was not said whether the gramophones played “Way down the Swanee River” or “Way down the River Torridge.”

The earliest occurrence of the phrase down the Swanee that I have found is from The Barrel, a short story by J. T. Jackson, published in the Birmingham Gazette (Birmingham, Warwickshire, England) of Tuesday 20^th July 1926—R.M.L.I. is the abbreviation of Royal Marine Light Infantry:

“The Limejooce Nivy, that’s wot the Yanks calls us,” remarked Signalman Jolly. “An’ I don’t wonder at it. I’d give a month’s pay for a pint of bitter this minnit.”
“There’s them as ’as beer on this lousy packet,” said Corporal Lightfoot of R.M.L.I. “Coalin’ ship in Bermuda, an’ nothin’ ter drink bat limejooce!”
[…]
“Now then, you scroungers,” shouted the bo’sun’s mate. “No wonder your gang’s down the Swanee. Get a move on. Lounging here when you know very well we’re trying to beat that big blighter over there!”
“It’s all very well ter race other ships when yer coalin’,” grumbled Corporal Lightfoot about half an hour later. “Wot say we ’ave a try fer that beer?”

The second-earliest occurrence of the phrase that I have found is from Pools Guide, by D. J. Blake, published in The Star (Sheffield, Yorkshire, England) of Saturday 18^th February 1939:

Will the sportsman (?) who sent in an unsigned letter last week complaining that I was “putting him in the workhouse” please note that only two newspaper forecasters gave Wednesday to draw at Chelsea last Saturday? “Looker-On” in the “Telegraph and Independent” was one—and I was the other.
Anyone who claims infallibility at this football forecasting business is not “kidding” anyone because he would be living in the South of France, with a cigar in each corner of his mouth if he could guarantee winners, instead of working for a living, but one tries to be helpful, and if you think you can do better just try it and see.
Results like Brentford’s away victory at Derby are absolutely impossible to forecast—and you only have to be wrong once to put your line down the swanee.

The phrase then occurs in the account of the annual meeting of the Royal Lancaster Infirmary Workpeople’s Committee, published in the Lancaster Guardian (Lancaster, Lancashire, England) of Friday 28^th April 1944:

It was stated by Mr. E. W. Holmes, one of the honorary surgeons, that unless the people were determined to take action, the fight against the Government’s proposed State Medical Service, there would be no Workpeople’s Committee, and no voluntary hospitals.
[…]
GOING “DOWN THE SWANEE.”
Canon R. O. Brimley said he whole-heartedly supported Mr. Holmes. He only hoped that voluntary hospitals would continue, and that there would not be State control of hospitals. He was afraid, however, that unless the advocates of voluntary hospitals were prepared to get together and to fight for their retention, they were going to be “down the Swanee,” as the saving was. (Laughter.)