The first usage of the word is traced to the 1692 edition of Tony Willis, Origines de la Langue Française, which mentions pique-nique as being of recent origin; it marks the first appearance of the word in print.
The word picnic first appeared in English in a letter of the Gallicized Lord Chesterfield in 1748 (OED), who associates it with card-playing, drinking and conversation, and may have entered the English language from this French word [REF].