Frequently used in the passive, the phrase to sell someone a pup means to swindle someone, especially by selling something of little worth on its supposed prospective value. And to buy a pup means to be swindled.
The expression is first recorded in 1901. That year, several newspapers gave its most likely origin; for example, the column From Day to Day of The Daily Express (Dublin, Ireland) of 6th May 1901 had:
The most conspicuous instance of an export duty is at the Cape of Good Hope, where there is £100 to be paid before an ostrich is allowed to leave the Colony. Even the export of ostrich eggs is taxed. But he would be a brave shipper who would pay duty on ostrich eggs. There is a poetical phrase in our language, “to sell a man a pup.” Puppies may look all right, but they develop signs of bad breeding later in life. Of ostrich eggs a very small proportion develop ostriches.
The British novelist, short-story writer and poet Rudyard Kipling (1865-1936) used the phrase in The Captive (1902), first published in the UK by The Illustrated London News of 27th June 1903:
‘It’s too bad,’ he says. ‘Johanna must have misunderstood me, or else I’ve got the wrong Dutch word for these blarsted days of the week. I told her I’d be out on Friday. Oah, da-am it all!’ he says. ‘I wouldn’t have sold old Van Zyl a pup like that,’ he says. ‘I’ll hunt him up and explain.’
The Sevenoaks Chronicle and Kentish Advertiser (Kent) of 19th November 1909 reported the following:
NEWSPAPER’S FAIR COMMENT.
The libel action brought by Mr. Charles Frederick Silver, licensee of the Railway Tavern, Jude street, Mildmay Park, against the “Hackney and Stoke Newington Recorder,” terminated in a verdict for the defendant.
The newspaper had ridiculed reports published that the plaintiff had been robbed of diamonds and jewellery, alleging that the papers reporting the theft had been “sold a pup,” and that the story of the alleged burglary was “ultra-bogus.”
The defendant, Mr. William Dunks Sievey, pleaded that the statements made in his paper did not exceed the limits of fair comment on a matter of public interest.
Mr. Justice Hamilton, in summing up, said it was a question for the jury whether the comment was fair, or defamatory and actionable.
The jury found for the newspaper, and judgment was entered accordingly.