keep under one's hat

Idioms and Phrases

Preserve the secrecy of something, as in I'll tell you about it if you promise to keep it under your hat . This usage alludes to hiding a secret in one's head, covered by a hat. [Late 1800s]

Related Words

• conceal
• deduct
• deny
• detain
• hide
• keep
• refuse
• resist
• retain
• suppress