Barbauld’s etiquette book A Legacy for Young Ladies Consisting of Miscellaneous Pieces in Prose and Verse was an important social resource. Like Miss Manners or Emily Post, Barbauld is sure that what she has to say is correct.
Barbauld’s explanation of “pic nic” then a new indoor dining style is positive. She writes that it’s a “very sociable way of making an entertainment” and requires each guest to bring something to the table and be conversational:
Pray, mamma, what is the meaning of pic- nic? I have heard lately once or twice of a pic-nic supper, and I cannot think what it means; I looked for the word in Johnson’s Dictionary and could not find it.
I should wonder if you had, the word was not coined in Johnson’s time*; and if it had, I believe he would have disdained to insert it among the legitimate words of the language. I cannot tell you the derivation of the phrase; I believe pic-nic is originally a cant [slang] word and was first applied to a supper or other meal in which the entertainment is not provided by any one person. Still, each of the guests furnishes his dish. In a pic-nic supper, one supplies the fowls, another the fish, another the wine and fruit, &c.; and they all sit down together and enjoy it.
See Anna Letitia Barbauld. Works of Anna Letitia Barbauld. Vol. 2. New York: 1826
*Samuel Johnson disliked English cognates for French words and did not include “picnic” in his dictionary (1755). Dining in the picnic style was already common among the Parisians but not among the English. Piquenique appeared in Menage’s Dictionnaire Du Etymologique De La Langue Françoise (1694).