also: ないしょばなし
noun
confidential talk; whispering; secret conversation
Rare term for a private or whispered conversation, often with a nuance of secrecy. The variant 内緒話 (ないしょばなし) is more common.
See also: 内緒話
二人は隅で内証話をしていた。
The two were having a confidential talk in the corner.
内証話が聞こえないように声をひそめた。
They lowered their voices so the secret conversation wouldn't be heard.
Compound of 内証 (ないしょう, 'secret' or 'confidential') and 話 (はなし, 'talk'). The spelling 内証 is a variant of 内緒, with 証 possibly used as ateji for the meaning 'proof' or 'evidence', but the exact derivation is uncertain.