Diamond
Middle English: from Old French diamant, from medieval Latin diamas, diamant-, variant of Latin adamans (see adamant).
wiktionary
From Middle English dyamaunt, from Old French diamant, from Late Latin diamas, from Latin adamas, from Ancient Greek ἀδάμας(adámas, “diamond”). Cognate with Spanish imán(“magnet”) and diamante, French aimant(“magnet”) and diamant, Italian diamante, and Portuguese ímã(“magnet”) and diamante.
Borrowed from Dutch diamant, used by Dirck Voskens who first cut it around 1700, presumably naming it by analogy with the larger Perl.
etymonline
diamond (n.)
mid-14c., diamaunt, diamond, "extremely hard and refractive precious stone made of pure or nearly pure carbon," from Old French diamant, from Medieval Latin diamantem (nominative diamas), from Vulgar Latin *adiamantem (which was subsequently altered by influence of the many Greek words in dia-), from Latin adamantem (nominative adamans) "the hardest metal," later, "diamond," from Greek adamas (genitive adamantos), name of a hypothetical hardest material, noun use of an adjective meaning "unbreakable, inflexible," a word of uncertain origin (see adamant (n.)).
From early 15c. as "person of great worth" (a sense also in Latin). From late 15c. as "geometric figure of four equal straight lines forming two acute and two obtuse angles." From 1590s as "playing-card stamped with one or more red diamonds." In baseball, "square space enclosed within the four bases," is American English, by 1875. As an adjective "resembling, consisting of, or set with diamonds," from 1550s.
