首根っこ
the scruff of the neck彼は少年の首根っこを押さえたHe seized the boy by the scruff of his neck.
back1
[名]1 C（人・動物の）背中（解説的語義）背a rounded backねこ背the lower back腰chronic back pain慢性的な背中の痛みat a person's ba...
on A's back
1 Ａ（人）におぶさって2 ((略式))Ａ（人）の首根っこを押さえて，Ａを支配下に置いて，悩ませて（⇒(flat) on one's BACK）get [be] on a person's ba...
