the mind > mental capacity > knowledge > hiding, concealing from view > privacy > [adverb] > in confidence (4)
in counsel: in private, in confidence. Obsolete.
Used, esp. parenthetically, to indicate that something is confidential or not to be communicated more widely: between ourselves, in confidence.
In a confidential manner, tone, etc.
Australian and New Zealand colloquial. just quietly: confidentially, between you and me.