scruff /skrʌf/ BrE AmE noun
[ Date: 1700-1800 ; Origin: scuff 'back of the neck' (18-19 centuries) , perhaps from Old Norse skoft 'hair of the head' ]
1 . by the scruff of the neck if you hold a person or animal by the scruff of their neck, you hold the skin, fur, or clothes at the back of their neck
2 . [countable] British English informal someone who looks untidy or dirty