爪つめを噛かむ癖くせ

expression

nail-biting habit

Refers to the habitual action of biting one's fingernails, often discussed as a nervous habit.

• 彼かれは緊きん張ちょうすると、爪つめを噛かむ癖くせが出でる。

  When he gets nervous, his nail-biting habit comes out.

• 爪つめを噛かむ癖くせを直なおしたい。

  I want to break my nail-biting habit.