nacreous (adj.)

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).