Idiosyncrasy

ˌɪd.i.əˈsɪŋ.krə.si

noun

A mode of behavior or way of thought peculiar to an individual.

Idiosyncrasy comes from the Greek word 'idiosynkrasia' meaning 'a peculiar habit of body' and is commonly used to describe unique characteristics or behaviors of individuals.

Also, it was an idiosyncrasy with me to distrust instinct, which had its roots in our animality.

T. E. Lawrence

Seven Pillars of Wisdom