You may be familiar with the old saying caveat emptor, nowadays loosely translated as "let the buyer beware." In the 16th century, this adage was imparted as a safeguard for the seller: allow the buyer to examine the item (for example, a horse) before the sale is completed, so the seller can't be blamed if the item turns out to be unsatisfactory. Caveat in Latin means "let him beware" and comes from the verb cavēre, meaning "to be on guard." Perhaps you've also heard caveat lector: "let the reader beware," a warning to take what one reads with a grain of salt. English retained caveat itself as a noun for something that serves to warn, explain, or caution. The word caution is another descendant of cavēre.