Samuel Foote’s The Nabob, now obscure, is the first linkage of picnic with the euphemism “nick-nack.” He used in the sense of dining en piquenique, which suggests familiarity. The alliterative corruption is meant to be humorous for those in the know of the trendy Parisian custom:
Janus. Time enough. —You had no particular commands, master Conserve?
Conserve. Only to let you know that Betsy Robins has a rout and supper on Sunday next.
Janus. Constant still, Mr. Conserve, I see. I am afraid I can’t come to cards, but shall be sure to attend the repast. A nick-nack, I suppose?
Conserve .Yes, yes; we all contribute, as usual: The substantials from Alderman Sirloin’s; Lord Frippery’s cook finds fricassees and ragouts; Sir Robert Bumper’s butler is to send in the wine, and I shall supply the desert.
Janus. There are a brace of birds and a hare that I cribbed this morning out of a basket of game.
Conserve. They will be welcome. [Act 1, sc. 2]
A nick-nack is a meal to which guests dined are expected to bring a share. Where Foote got nick-nack from is a mystery. Perhaps he coined it. But by not using picnic, Foote lost his chance for linguistic fame. Ironically, an anonymous poem, “Samuel Foote,” appearing in a journal titled The Pic Nic (1803), remembered Foote as A satirist without gall, a random wit,/That shot his bolt, not caring where it hit. By then, Foote was dead for twenty-six years, and the picnic was entering the popular vocabulary. As a euphemism for picnic, Nick-Nack n is buried in The Nabob.
See Foote, Samuel. The Nabob; a Comedy in Three Acts. London, 1772