Philip Dormer Stanhope, Lord Chesterfield, is the second person to use picnic in English and spell it in a modern way. His son Philip, living in Leipzig, wrote that he attended a picnic gathering at Madame Valentin’s salon, but this 1748 letter is lost.
Chesterfield was familiar with the salon assembly but not a picnic. “I know that you go sometimes to Madame Valentin’s assembly,” he wrote, “What do you do there? Do you play or sup, or is it only la belle conversation?” Philip’s reply surprised Chesterfield, who answered, “I like the description of your picnic, where, I take it for granted, that your cards are only to break the formality of a circle, and your symposium is intended more to promote conversation than drinking.” Though Chesterfield had many French contacts, he was apparently unfamiliar with the Parisian custom of pique-nique.
In fact, picnic was an unfamiliar word among the English. It is omitted in Nathan Bailey’s An Etymological Dictionary (1721/1756) and Samuel Johnson’s A Dictionary of the English Language (1755). It was not until 1802 that the word was purposely publicized by the Pic Nics, a London-based dining/theatrical/dining/gambling club.
Chesterfield’s letter was private and published along with 262 others in the posthumous edition of The Letters of Philip Dormer Stanhope Letters in 1774. Chesterfield died in 1773 without ever mentioning picnic again.
See: The Letters of Philip Dormer Stanhope, Earl of Chesterfield to His Son Philip Stanhope, Esq., two vols. (London: J. Dodsley, 1774); The Letters of Philip Dormer Stanhope, Earl of Chesterfield to His Son on the Fine Art of Becoming a Man of the World and a Gentleman (1774). Edited by Oliver H. G. Leigh. Washington & London: M. Walter Dunne, 1901.; https://archive.org/stream/letterstohissono01chesuoft/letterstohissono01chesuoft_djvu.txt