Word ‘Carat’, a weight measuring unit came from ‘Carob’.
(Image: The Australian Carob ; Gemological Institute of America )
Carob Seeds, found on Carob Trees are seeds full of Sugar. African people up until 17th century used to eat them to gain sugar in the blood. One carob seed is 0.2 grams and each seed is almost of same weight. So, somebody decided to use them against measuring diamond’s weight as 200 milligram as 1 carat.
Today, instead of using Carob seeds, we use equivalent weight of slab to measure the weight of a diamond.
Source: What Does the Word Carat Have to Do with Carob Seeds?