Picnic Etymology:
1748 (in Chesterfield's "Letters"), but rare before c.1800 as an Eng. institution, from Fr. piquenique (1692), perhaps a reduplication of piquer "to pick, peck," from O.Fr. (see pike (2)), or the second element may be nique "worthless thing," from a Gmc. source. Originally a fashionable pot-luck social affair, not necessarily out of doors. Figurative sense of "something easy" is from 1886.
Online Etymology Dictionary, © 2001 Douglas Harper