/ˌɪd.i.əˈsɪŋ.krə.si/

a strange or unusual habit, way of behaving, or feature that someone or something has:

• She often cracks her knuckles when she's speaking - it's one of her little idiosyncrasies.

a strange or unusual habit, way of behaving, or feature:

• One of her many idiosyncrasies is always smelling a book before opening it.

We human are strange, we all have unusual habit.