Swanee, n. — Green’s Dictionary of Slang

Swanee n.

In phrases

go up the Swanee (v.)

to be ruined, to become bankrupt.

1970		C. Brown Down All the Days 70: Married now are yeh! [...] free to fornicate with any cat, dog or divil! She’s gone up the Swanee now for sure.
1981		B. Hoy ‘Uncle George’ in Wright Cockney Dial. and Sl. (1981) 109: Britannia’s gawn right up the Swanee, / Wiv closed minces we foller the oafs. / We’re in bad two-an’-eights / Buckle to, mi ol’ mates / And for cryin’ aht lahd use yer loafs!
2021		A. Parks April Dead 351: ‘Two hundred and seventy quid down the Swanee’.

up the Swanee (adj.) [generic use of up the river under river n. to imply any form of trouble + ref. to the Al Jolson song ‘Swanee’; ? ult. Suwannee River, Georgia/Florida, USA]

ruined, destroyed, broken, out of order.

2005

S. Bubb Helping Teachers Develop 42: Thirty minutes to go, lesson plan up the Swanee, no resources!