A sturdy metal container for storing valuables, money, or important documents. Often used in historical or formal contexts; in modern everyday language, 金庫 (きんこ) is more common for a safe.
I put the account books in the safe and locked it.
Compound of 金 (きん, 'metal') and 櫃 (き, 'chest, box'). The exact historical derivation is uncertain, but the word has been used since pre-modern times to refer to a lockable metal container.
