also weiə-, Proto-Indo-European root meaning "to turn, twist, bend," with derivatives referring to suppleness or binding.
It is the hypothetical source of/evidence for its existence is provided by: Avestan vaeiti- "osier;" Greek itea "willow," iris "rainbow;" Latin viere "to bend, twist," vitis "vine;" Lithuanian vytis "willow twig;" Old Irish fiar, Welsh gwyr "bent, crooked;" Polish witwa, Welsh gwden "willow," Russian vitvina "branch, bough;" Old English wir "metal drawn out into a fine thread."
1590s, "type of shellfish that yields mother-of-pearl," from French nacre (Old French nacaire, 14c.), from Italian naccaro (now nacchera), possibly from Arabic naqur "hunting horn" (from nakara "to hollow out"), in reference to the shape of the mollusk shell. Meaning "mother-of-pearl" is from 1718. The French adjectival form nacré was applied in English to decorative objects iridescent like mother of pearl (1895).