Green’s Dictionary of Slang

1. any day of the week without work, and thus money.

1707		N. Ward Wooden World 57: It’s only his own Bags that would thrive by the Project, he getting more by one Bannian-Day, than many others.
1789		Norfolk Chron. 1 Aug. 2/1: The King [...] asked what the seamen dined upon that day; and being answered it was a Banyan day.
1793		Hants. Chron. 29 Apr. 4/1: The Soldier’s Litany [...] May we all be deliver’d [...] From the want of a blanket and holes in our tent; From hospital-ships, banyan-day and Lent.
1831		Navy at Home II 14: Florence, whose mess was famous for its puddings (onbanyan days).
1835		G. Kent Modern Flash Dict. 4: Banyan day – Saturday, when there’s nothing left to eat.
1836		Marryat Japhet 255: ‘May your honour never know a banyan day,’ replied the sailor.
1848		Flash Dict. in Sinks of London Laid Open [as cit. 1835].
1858		C. Abbey diary 1 Aug. in Gosnell Before the Mast (1989) 142: An empty stomach (today is ‘banyan’ day).
1861		(con. 1840s–50s) H. Mayhew London Labour and London Poor I 360/1: Many a banyan day I’ve had in my little room – upon a wet day – aye, and other days too.
1866		J. Greenwood Little Ragamuffin 299: It’s always the same; meat to-day, banyan to-morrow – no certainty.
1876		C. Hindley Life and Adventures of a Cheap Jack 292: They may never have short allowance – ban yan days; or a southerly wind in the Bread Basket.
1882		W. Besant All Sorts and Conditions of Men II 109: The Professor was already come to the period of waist-tightening, which naturally follows a too continued succession of banyan days.
1886		Referee 2 May in Ware (1909) 18/2: Those were the halcyon days of British industries. The banyan days have been with the miners since then, and seem likely to stay.
1900–10		Stephens & O’Brien Materials for a Dict. of Aus. Sl. [unpub. ms.] 9: BANYAN DAY: Friday is so-called in the bush. Any day of starvation or short diet is also called a Banyan day.
1909		J. Ware Passing Eng. of the Victorian Era 18/2: Banyan Day (Middle-class). No meat; only ‘bread and cheese and kisses’ through twenty-four hours.

2. in fig. use, an unfortunate, ill-fated day.

1861

Bell’s Life in Sydney 1 June 3/2: It was a banyan day for me, / When I met Polly Liddle, / For had I been safe out at sea, / Poor Jack she could not diddle.

3. (Aus.) Friday, esp. in prisons.

1865		T. Archer Pauper, Thief and Convict 39: ‘This is pudding day’ – the day, that is to say, which is known at sea as ‘banyan,’ and it has been celebrated by the substitution of suet pudding and treacle for the ordinary meat, bread, and vegetables.
1935		A.J. Pollock Und. Speaks 5/1: Banyan day, Friday, no meat (prison).
1945		Baker Aus. Lang. 82: Banyan day, the name by which Friday was known in the bush a generation or so ago. [...] Stephens and O’Brien [in 1900–10] note ‘Any day of starvation or short diet is also called a banyan day’.