首根っこ

くびねっこ【首根っこ】

¶ネコの～をつかむ

catch a cat by the scruff of the neck.

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くびねっこ【首根っこ】

the scruff (of the neck).

●首根っこを押さえる hold sb by the scruff of the neck; render sb immobile; 〔比喩的に〕 get sb securely in one's grip; get sb on the hip [《口》 over a barrel].