"Hot-blooded" is an English idiom meaning passionate, easily excited, or quick tempered. Its first known use is in William Shakespeare’s comedy The Merry Wives of Windsor. The word should not be confused with scientific terms cold-blooded or warm-blooded, although it can also be used to refer to a certain type of horse.
One common use of this adjective is to describe someone who is extremely passionate or aroused, though it can also be used to describe a person who is impetuous and quick-tempered. For example, in 1837, American author Washington Irving described a character as “a fiery hot-blooded youth” in The Adventures of Captain Bonneville. This character, Kosato, killed the chief of his tribe and ran away with the chief’s wife. After taking refuge with the peaceful Nez Pierce tribe, he longs for the adventure of battle.
The type of character Irving created is a prime example of someone who is "hot-blooded." A similar idiom is the sentence “it made his blood boil.” Primarily heard in the U.S., this particular saying can be used for any situation which angers or enrages the subject.
William Shakespeare has perhaps the first recorded use of the idiom in a comedy he wrote around the year 1600. In act five, scene five of The Merry Wives of Windsor, the main character, Falstaff, is hoping to seduce two married women. In a soliloquy, he says “Now, the hot-blooded gods assist me!” Just a few years later, Shakespeare used the adjective again in act two, scene four of the tragedy King Lear.
This phrase can also be used to refer to certain smaller, lighter breeds of horses. Arabian, Thoroughbred, Barb, and Akhal-Teke horses are all considered to be hot-blooded. Although they may not be as strong as other breeds, they are known for their exceptional speed and stamina. These types of horses are used frequently as racehorses.
The term hot-blooded is often confused with the similar sounding phrases warm-blooded and cold-blooded, but they are completely different. While the idiom refers to a certain temperament or a type of horse, warm-blooded and cold-blooded refers to an animal’s body temperature in relation to its environment. Mammals, birds, and other warm-blooded animals regulate their body temperature by creating heat in cold environments and releasing it in warm environments. Cold-blooded animals such as reptiles remain basically the same temperature as the air around them.