As thick as thieves

Meaning

Very close or friendly with someone.

Usage

Used to describe warm, trusting pairs.

Origin & History

Origins and dates here are approximate summaries. Many idioms have disputed or unknown origins, and not every date has been checked against a historical dictionary, so treat specific dates and stories as a starting point rather than a citation.

Old proverb referencing conspirators.

Found in literature from the 18th century.