mid-14c., ambre grice "ambergris; perfume made from ambergris," from the phrase in Old French (13c.) and Medieval Latin, from Arabic 'anbar "ambergris, morbid secretion of sperm-whale intestines used in perfumes and cookery" (see ambergris), which was introduced in the West at the time of the Crusades. Arabic -nb- often is pronounced "-mb-."
In Europe, amber was extended to fossil resins from the Baltic (late 13c. in Anglo-Latin; c. 1400 in English), and this has become the main sense as the use of ambergris has waned. Perhaps the perceived connection is that both were found washed up on seashores. Or perhaps it is a different word entirely, of unknown origin. Formerly they were distinguished as white or yellow amber for the Baltic fossil resin and ambergris "gray amber;" French distinguished the two substances as ambre gris and ambre jaune.
Remarkable for its static electricity properties, Baltic amber was known to the Romans as electrum (compare electric). Amber as an adjective in English is from c. 1500; as a color name 1735. In the Old Testament it translates Hebrew chashmal, a shining metal.