Region: UK | Usage example: The new policy was criticized as a way for executives to feather their nests.

Feather your nest

Meaning

Enrich oneself, often at others' expense.

Used critically about self-serving behavior.

Origin notes can vary by region and source; this page gives the commonly reported explanation and usage context.

Birds lining nests with feathers for comfort.

17th-century English idiom with moral overtones.