frivolity
佻 centers on a lack of seriousness or weight: frivolity, lightness, and a tendency to treat things without proper gravity.
佻 combines the person radical 亻 with 兆, which likely contributes the sound and carries a sense of lightness or omen. The exact historical development is uncertain.
A person 亻 beside 兆, a shape associated with a sign or omen. Picture someone treating even serious omens lightly, with a frivolous, carefree attitude.
For チョウ, imagine a frivolous person named Chou who never takes anything seriously: Chou -> チョウ, and their light-heartedness is the core of 佻.