carat

英文詞源

carat

carat: [16] The carat gets its name from the use of carob beans as standard weights for measuring the heaviness of small quantities. The Greek name for the elongated seed pod of the carob tree was kerátion, a derivative of kéras ‘horn’ (related to English horn). This passed into Arabic as qīrāt, where it became formalized in a system of weights and measures as ‘four grains’. It passed into English via Italian carato and French carat.
=> horn

carat (n.)

also karat, mid-15c., from Middle French carat "measure of the fineness of gold" (14c.), from Italian carato or Medieval Latin carratus, both from Arabic qirat "fruit of the carob tree," also "weight of 4 grains," from Greek keration "carob seed," also the name of a small weight of measure (one-third obol), literally "little horn" diminutive of keras "horn" (see kerato-).

Carob beans were a standard for weighing small quantities. As a measure of diamond weight, from 1570s in English. The Greek measure was the equivalent of the Roman siliqua, which was one-twentyfourth of a golden solidus of Constantine; hence karat took on a sense of "a proportion of one twentyfourth" and became a measure of gold purity (1550s). Eighteen carat gold is eighteen parts gold, six parts alloy. It is unlikely that the classical carat ever was a measure of weight for gold.