You use these words on a regular basis, but their etymology may surprise you.
Under ancient Roman law, addiction referred to the legal surrendering of an individual as a slave to a master. Ultimately, the term addict became associated with habitual behavior that made a person a slave to something else; this included the craving of substances such as drugs or alcohol.
Carat, the standard unit of weight for precious stones, derives from the Greek word for carob seeds, "keraton." Apparently, fully grown carob seeds have a consistent weight from seed to seed (approximately 200mg), which made them a handy item to determine the weight of small objects, such as diamonds, on a balance scale.
After examining plant matter under a microscope, early modern scientist Robert Hooke coined the word cell to refer to the smallest unit of life because plants' cellular structure resembled monks' cells (living quarters) in a monastery.
Although we commonly think of ketchup as a tomato product, historically the term derives from a Chinese fish sauce called ke-tsiap. English travelers likely brought the recipe back from Malaysia. By the mid-eighteenth century, "ketchup" or "catsup" was a common staple in Britain and its American colonies. Tomatoes weren't part of the recipe until the 1790s, partly due to a common English/American belief that tomatoes were unsuitable for human consumption.