Don't Get Tired Defining Knackered

Knackered is derived from the past participle of knacker, a slang term meaning "to kill," as well as "to tire, exhaust, or wear out." The origins of the verb knacker are uncertain, but the word is perhaps related to an older noun knacker, which originally referred to a harness-maker or saddlemaker, and later referred to a buyer of animals no longer able to do farmwork (or their carcasses) as well as to a buyer of old structures. The origins of the noun knacker, however, remain obscure. Knackered is used on both sides of the Atlantic but is more common among British speakers.