Floss
mid 18th century: from French (soie) floche ‘floss (silk)’, from Old French flosche ‘down, nap of velvet’, of unknown origin.
wiktionary
Uncertain. Perhaps from Middle English *flos (attested in Middle English Flosmonger(a surname)), related to English fleece. Alternatively from French floche(“tuft of wool”), from floc, from Old French flosche(“down, velvet”), from Latin floccus(“piece of wool”), probably from Frankish *flokkō(“down, wool, flock”), from Proto-Germanic *flukkô(“down, piece of wool, flock”), from Proto-Indo-European *plewk-(“hair, fibres, tuft”). Cognate with Old High German flocko(“down”), Middle Dutch vlocke(“flock”), Norwegian dialectal flugsa(“snowflake”), Dutch flos(“plush”) (tr=17c.).
From dialectal flosh(“a flush, stream of water, sluice”), from Middle English flosche, flusche, flasche, flaske(“a watery or marshy place, swamp”), perhaps from Old French flache, from Middle Dutch vlacke(“a flat area, plain”). Compare also German Floss(“a float”).
Origin obscure. Perhaps of North Germanic origin. Compare Norwegian flos, flus(“rind, scale, strip peeled off”).
etymonline
floss (n.)
"rough silk," 1759, of uncertain origin, perhaps from French floche "tuft of wool" (16c.), from Old French floc "tuft, lock," from Latin floccus "tuft of wool," a word of unknown origin. Or from a dialectal survival of an unrecorded Old English or Old Norse word from the root of fleece (n.). Compare the surname Flossmonger, attested 1314, which might represent a direct borrowing from Scandinavian or Low German. In "The Mill on the Floss" the word is the proper name of a fictitious river in the English Midlands. Meaning "fine silk thread" is from 1871, short for floss silk (1759). Dental floss is from 1872; the verb floss in reference to use of it is from 1909. Related: Flossed; flossing.
