Origin of the Word Picnic
There are at least a couple of stories about the origin of the word 'picnic'. It is said to be the abbreviation of the term 'pick a nigger', which referred to an outdoor community festive gathering during which families used to enjoy their food from home-packed lunch boxes, while an arbitrary selected black man was hanged for the diners' entertainment. It is also said that it is derived from the term 'pick-a-nig', which was actually a gathering for slave traders and their families back in the 17th/18th centuries. They would get together for a big festive party, called a 'pick-a-nig', after the end of slave trading.
However, though some of the historic photographs of lynching show families with picnic baskets, there is no truth in those stories from an etymological viewpoint. The picnic is derived from a French word, ' picque-nique', which first appeared in the seventeenth-century dictionary.
As for how the French came to this new term, it was likely invented by joining the common form of the verb 'piquer' (meaning "to pick" or "peck") with 'nique,' possibly an obsolete word meaning "a trifle" or merely a nonsense rhyming syllable coined to fit the first half of this new palate-pleaser.
Though it may have appeared in a 17th-century dictionary as "pique-nique", the actual usage began as "pique un niche" meaning to "pick a place," where family or friends could enjoy a meal together in a pastoral setting, away from the locality. Gradually, the term morphed into "pique-nique" and after years of usage entered the official French language.
The first documented appearance of the term outside the French language occurred in 1748, but the word picnic was rarely used in English prior to 1800 or thereabouts. However, even then, the word still was not being used in America.