Today, the word picnic refers to a meal taken outdoors as part of an excursion, ideally in scenic surroundings, such as a park, lakeside or rustic settings, usually occurring in the summer time.

The word comes from the French word ‘pique-nique’, whose earliest usage in print is in the 1692 edition of Tony Willis, ‘Origines de la Langue Francaise’ (Beginnings of the French Language). The term described a group of people dining in a restaurant who brought their own wine. According to some dictionaries, the French word ‘pique-nique’ is based on the verb ‘piquer’, which means ‘pick’, ‘peck’ or ‘nab’ and the rhyming addition of ‘nique’, means ‘thing of little importance’.

The word ‘picnic’ first appeared in English in a letter from Lord Chesterfield (1694-1773) in 1748 referenced in the Oxford English Dictionary. He was a British statesman, diplomat, and man of letters, and an acclaimed wit for his time. Dictionaries agree it entered the English language as a respelling of the French word ‘pique-nique’.

More Info: en.m.wikipedia.org