From the Arabic for "hunting horn", it's another name for mother-of-pearl
... (Another difference 
is that the plural of makor as "source" is mekorot, ... the word "nacre", meaning "
mother of pearl", which has the following ... from Italian naccaro (now nacchera), 
possibly from Arabic naqur "hunting horn" (from nakara "to hollow... [DOC] [TLE] nacre (n.) - Online Etymology Dictionary [PAR] 1590s, "type of shellfish that yields mother-of-pearl," from Middle French nacre (
14c.