a peculiar trait; idiosyncrasy; a quirk
Often implies a slightly difficult or stubborn personality trait, not just any characteristic. Commonly used in phrases like 一癖ある or 一癖も二癖もある.
He is a person with a peculiar streak.
That author's works are full of quirks.
Standard kanji spelling.
Kana spelling is common in everyday writing.
Compound of 一 (one) and 癖 (habit, trait). The exact historical derivation is uncertain, but it likely developed from the idea of 'one peculiar habit' to mean a distinctive, often difficult, personality trait.