Knacker

Knacker (v.)'to kill, castrate' (1855), apparently from knacker (n.) 'one who slaughters old or sick horses' (1812). This is probably the same word as the earlier knacker/ nacker 'harness-maker' (1570s), which survived in 18c. The sense extension is perhaps because knackers supplied farmers general help with horse matters, including disposing of dead ones. The word is of uncertain origin, possibly from a dialectal survival of a Scandinavian word represented by Old Norse hnakkur 'saddle,' related to hnakki 'back of the neck,' and thus possibly related to (n.). Most often used in weakened sense of 'to tire out' (1883) and usually encountered in its past tense,.

柯林斯高阶英汉双解学习词典 N-COUNT 废马屠夫（买下老马并将其屠宰以获取其肉、骨、皮的人） A knacker is someone who buys up old horses and then kills them for their meat, bones, or leather. Beyond the beyond ps1. Her horse was a show jumper whom the family rescued from the knacker's yard. The evil within trophy guide. Knacker (sense 2 of the noun) may be from dialect knacker ‘castanet’, from obsolete knack ‘make a sharp abrupt noise’, of imitative origin. It is unclear whether the verb represents a figurative use of ‘slaughter’, from knacker (sense 1 of the noun), or of ‘castrate’, from knacker (sense 2 of the noun).