To lower, to reduce. The N.E.D. gives examples of falling a gun (1692), falling the eyelids (1748), falling vessels in a canal (1795).

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1806.  

        I’ll sooner throw my ware away
Than fall a groat from what I say.
Mass. Spy, July 9: from the Luzerne Federalist.    

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1820.  “I killed a hundred of them [snakes],” said he, “in a few minutes, each as large as my leg.” “I do not dispute it,” replied his friend, “but would be better satisfied if you would fall a snake or two.”—James Hall, ‘Letters from the the West,’ p. 349 (Lond.). (Italics in the original.)

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1847.  “Can’t you fall a dollar?” “Perhaps I might, if I could make up my mind to undertake your school.”—D. P. Thompson, ‘Locke Amsden,’ p. 59 (Boston).

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1855.  “I say I saw twenty-five, and I will not fall another snake.”—Mr. Benton’s version of the story: Cong. Globe, p. 483 (Jan. 31).

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1880.  [Joe Meek said he had walked about 385 miles] in eight days, and without anything to eat except one thistle-root…. I replied: “That was a most extraordinary adventure, Joe; and, while I don’t pretend to question your veracity in the least, don’t you really think you might safely fall a snake or two in the distance?”—Peter H. Burnett, ‘Recollections and Opinions of an Old Pioneer,’ p. 159.

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