Green’s Dictionary of Slang

not care a farthing v.

to not care at all.

1695		Congreve Love for Love I i: Your being in love with a lady that did not care a farthing for you in your prosperity.
1702		Farquhar Twin-Rivals I i: As for my brother, he don’t care a farthing for me.
1709		R. Steele Tatler No. 50 n.p.: I don’t care a Farthing for you.
1719		in D’Urfey Pills to Purge Melancholy III 269: What care I, what care I one Farthing.
1749		Smollett (trans.) Adventures of Gil Blas (1822) I 131: The saucy rascal swore she did not care a farthing for me!
1770		Foote Lame Lover in Works (1799) II 65: He knows I don’t care a farthing for him.
1794		Sporting Mag. Jan. III 204/1: When people have money enough to go to war, they need not care a farthing for a pretence.
1825		‘Kickaraboo’ Universal Songster I 29: You care no one farthing for kickaraboo.
1840		Carlisle Patriot 8 Feb. 4/1: For old Hatton-garden / We don’t care a farden.
1859		G.A. Sala Twice Round the Clock 130: Letters of introduction from people I didn’t know, or didn’t care five farthings about.
1864		G.A. Sala Quite Alone III 131: Them furriners don’t seem to care a brass farden what becomes of their own flesh and blood.
1877		Newcastle Wkly Courant 6 July 6/2: ‘I don’t care a brass fardin’ who knows’.
1894		‘Price Warung’ Tales of the Early Days 241: The poor sinner at Macquarie Harbour, who told Surgeon Barnes that once he was flogged he did not care a brass farden what became of him.
1896		‘Mark Twain’ Tom Sawyer, Detective Ch. XI: Brace Dunlap, who’s been sniveling here over a brother he never cared a brass farthing for.
1936		‘Josphine Tey’ Shilling for Candles 47: ‘Hooey! [...] not one of us cared a brass farthing for her’.