From Late Latin flascō, flasca (“bottle, container”), from Old Frankish *flaska (“bottle, flask”), from Proto-Germanic *flaskǭ (“bottle”), from Proto-Germanic *flehtaną (“to plait”), from Proto-Indo-European *plek- (“to weave, braid”). Akin to Old High German flasca (“flask”), Old English flasce, flaxe (“bottle”). Doublet of flacone. More at flask.