A knacker (/ˈnækər/), knackerman or knacker man is a person who removes and clears animal carcasses (dead, dying, injured) from private farms or public highways and renders the collected carcasses into by-products such as fats, tallow (yellow grease), glue, gelatin, bone meal, bone char, sal ammoniac,[1] soap, bleach and animal feed.
The kinds of animal processing which can occur at knackeries are defined by law, for example, in Australia by the Commonwealth Meat Inspection Act 1983.
[6] "Knackered" meaning tired, exhausted or broken in British and Irish slang is commonly used in Australia, Ireland, Newfoundland, New Zealand, and the United Kingdom.
[7][8] The British satirical magazine Private Eye often refers to senior police figures as "Inspector Knacker" or the police force in general as "Knacker of the Yard", a reference to Jack "Slipper of the Yard" Slipper.
[11][12] "Knackers" is also a British/Australasian vulgar slang for testes,[13] although this usage may be derived from nakers – small medieval kettle drums which were typically played in pairs suspended from a belt around the waist.