Fetching details from the dictionary...

secrecy; confidentiality; privacy; secret
one's circumstances (esp. fiscal)
inner realization; personal enlightenment
kitchen
転職の準備は内証で進めているところだ。
I am making preparations to change jobs in secret.
この話は内証にしておいてほしいと頼まれた。
I was asked to keep this matter confidential.
内証の貯金が見つかって妻に問い詰められた。
My secret savings were discovered and my wife confronted me.