noun which may take the genitive case particle 'no', adverb, noun
private; confidential; internal; within a closed group
Used for matters kept within a family, company, or close circle; not for public disclosure. Often implies informality or off-the-record handling.
この話は内々にしておいてください。
Please keep this matter confidential.
It's an informal gathering, so please feel free to come.
人事のことはまだ内々で進めている。
We're still handling the personnel matter internally.