Dates to 1899, American humor origin, originally featuring a woman upset by a man's cigar smoking. Cigar often removed in later versions, coffee added in 1900. Incorrectly attributed in Consuelo Vanderbilt Balsan, Glitter and Gold (1952).
See various early citations and references to refutations at “If you were my husband, I’d poison your coffee” (Nancy Astor to Churchill?) http://www.barrypopik.com/index.php/new_york_city/entry/if_you_were_my_husband_id_poison_your_coffee_nancy_astor_to_churchill, Barry Popik, The Big Apple,' February 09, 2009
Early examples include 19 November 1899, Gazette-Telegraph (CO), "Tales of the Town," p. 7, and early attributions are to American humorists Marshall P. Wilder and De Wolf Hopper.
Churchill by Himself: The Definitive Collection of Quotations, by Richard Langworth, PublicAffairs, 2008, p. 578.
The Yale Book of Quotations, edited by Fred R. Shapiro, New Haven, CT, Yale University Press, 2006, p. 155.
George Thayer, The Washington Post (April 27, 1971), p. B6.
Misattributed
Variant: Lady Nancy Astor: Winston, if you were my husband, I'd put arsenic in your morning coffee.
Winston Churchill: Madam, if you were my wife, I'd drink it.
