The term "knackered" (British slang for tired or exhausted) may have derived from the term "knacker" (a slang term meaning "to kill," but also "to tire, exhaust, or wear out." [1]) And the origin of the term "knack" itself is "probably related to obsolete knack ‘sharp blow or sound’, of imitative origin (compare with Dutch knak ‘crack, snap’)" [2]
[1] https://www.merriam-webster.com/dictionary/knackered
[2] Google's Oxford Languages' etymology