Comprehensive resource for understanding and mastering English idioms
The idiom "dog tired" means to be extremely exhausted or worn out, often to the point of being too drained to continue working or doing anything else. It can also mean feeling overworked or stressed out.
The idiom "dog tired" has been in use since at least the early 1900s. Its exact origins are unclear, but it may have derived from the idea of a dog that is so exhausted from running or playing that it can barely move. Over time, the phrase has come to be used figuratively to describe a person who is extremely tired, whether due to physical activity or emotional stress.