The word picnic in French is pique-nique, and while pique may mean "pick", nique's definition of "worthless item" is not entirely accurate. It was corrupted over the centuries from niche, "spot" (as in "pick your own spot") and people modified it to make it rhyme. Anyway, pique comes from the Old French word piquer, meaning "to pierce", specifically with a pike or sword (which is definitely "picking" something; also the root of English pick). This might be from a Latin word like piccare, which meant "to sting", but nobody's quite sure. Niche, meanwhile (also a word in English, of course) has several debated etymologies, but the most likely explanation is that it comes from the Latin word nidus, meaning "nest", which would come from Proto-Italic nizdos and Proto-Indo-European nisdos, with the same meaning. So, etymologically speaking, a picnic can be "piercing nests".
Adam Aleksic, a leading contender for valedictorian of his high school, is a 208-month-old boy with disturbing interests in etymology, vexillology, geography, and law. Adam would like to one day visit Tajikistan and just won an essay contest on linguistics!
The Etymology Nerd