dog-tired

The compound "dog-tired" is a vivid example of a metaphorical idiom in English. The first element, "dog," does not refer to the animal's specific traits but leverages the cultural perception of a dog as a creature that can become utterly exhausted after vigorous activity, such as hunting or working. The second element, "tired," comes from an Old English verb meaning to fail or become weary. The phrase likely originated in the 18th or 19th century, drawing a direct comparison to the complete physical depletion observed in hard-working dogs, thus creating a powerful and enduring metaphor for human exhaustion.

Structure: dog (dog) + tired (tired) - dog: (Origin: Old English docga; Role: Noun used attributively to form a compound, implying a characteristic or comparison) - tired: (Origin: Old English tēorian (to tire, fail); Role: Adjective root meaning weary or exhausted)