forty to the dozen, adv. — Green’s Dictionary of Slang

forty to the dozen adv.

also fourteen to the dozen, thirteen to the dozen, twenty to the dozen

[SE phr. nineteen to the dozen]

extremely fast; often as talk forty to the dozen.

1890		B.L. Farjeon Mystery of M. Felix I 236: He run against me, he did, and I sed, ‘Who are yer pushing of?’ He didn’t say nothink, but walked off forty to the dozen.
1907		Chums 26 June 902: The lady talked at the rate of thirteen to the dozen.
1910		Wodehouse Psmith in the City (1993) 111: Old Bick was shooting it out fourteen to the dozen.
1911		A. Bennett Hilda Lessways Bk V Ch. ii: Louisa was hidden in the kitchen, doubtless talking fourteen to the dozen with the cook.
1977		S. Galvin Operation Sadie 41: Joe was at my bedside [...] chatting away twenty to the dozen, hardly letting me get a word in .