Idiosyncrasy (noun)

A peculiar habit, behavior, or trait that is unique to an individual, especially one that is strange or unusual.

Origin:

The term 'idiosyncrasy' originated in the 17th century and is derived from the greek words 'idios' meaning 'personal' or 'private' and 'sunkrasis' meaning 'disposition' or 'mixture'.

Examples:

1. She has a distinct idiosyncrasy of tapping her foot whenever she's deep in thought.
2. He has an idiosyncrasy of speaking in a particular accent when he's angry.
3. Her idiosyncrasies made her stand out in a crowd, but they also made her endearing.
4. He had a quirky idiosyncrasy of always wearing a hat, no matter the occasion.
5. Her idiosyncrasies were a source of both amusement and frustration for those around her.