butt out

主人公のkid lawyer、Theoは知人の従兄の不法移民者が殺人事件の容疑者を目撃したと聞き、面談します。
“He wants to know why he should trust you,” Julio said. Theo was thankful for the interpretation because he’d understood almost none of the Spanish.
He said, “Look, Julio, how about a quick review? He came to you, you came to me, and now I’m here. I didn’t start this process. If he wants to leave, then good-bye. I’ll be happy to go home.” It was tough talk and it sounded pretty strong in English. Julio passed it along in Spanish, and the cousin glared at Theo as if he’d been insulted.
Theo did not want to leave. He knew he should. He knew better than to get involved. He’d been telling himself to butt out, but the truth was that Theo relished being exactly where he was at that moment.
"butt out" は初めて見る表現ではないと思いましたが、意味が直ぐには分からないので辞書を見ます。
・Oxford English Dictionary: North American informal Stop interfering: anyone who tries to cut across our policies should butt out
・Macmillan Dictionary: used for telling someone rudely to go away or not get involved in something: It’s my problem, so butt out!
・Cambridge Dictionary of American Idioms: to not get involved in something Teens usually think their parents should just butt out of their lives.
思い出しました、かなり前に（4/11/2008）、"butt out" とは反対の意味の "butt in" を "horn in" と共に取り上げていました。