His last submission to the New Yorker was about the OED's entry on 'blanket', which said that Thomas Blanket, 'to whom gossip attributes the origin of the name, if he really existed, doubtless took his name from the article.' Cuppy laid into the Oxford English Dictionary, which is as sloppy an institution as you'd assume to be honest, firstly for presuming that the well-documented Bristolian corn merchant didn't exist and second for thinking that he would have been such an idiot that he wouldn't have been able to think of a surname until 1339 when, already prosperous, he set up a cloth-producing business and saw blankets emerging from his factory. Cuppy showed that there were plenty of Bristolian Blankets, and that it was much more likely he was one of them than that he named himself after some woollen goods.
The New Yorker returned the piece. They thought it was funny but the editor Katharine S White felt that made up history was confusing and not really their sort of thing. The super-fastidious Cuppy was struck a terrible blow. He took some weeks to gather himself and then replied:
I hate to clutter up your mail, but I did want you to know (just for the record) that it wasn't a 'made up' piece at all. You wouldn't think so if you knew of the ungodly amount of actual physical toil I went through with it, such as getting information form the British Museum and reading the archives of the city of Bristol. As it stands, it is a contribution to history of the most authentic nature--but I thought I would make it funny, too. I intended it simply and solely as a few pertinent facts set down as lucidly as possible in order to right a great wrong, the smothering of Thomas Blanket (which now seems to have succeeded, and the truth will die with me).