eccentric habit; odd quirk
A formal or literary term for a peculiar personal habit or idiosyncrasy.
He has many eccentric habits that surprise those around him.
The writer's eccentric habits are reflected in his works.
More casual and common way to say 'strange habit'.
Compound of 奇矯 (kikyō, 'eccentric') + な (attributive) + 癖 (heki, 'habit'). The exact derivation of 奇矯 is uncertain; it is a Sino-Japanese word.