in confidence

1. Also, in strict confidence. Privately, on condition that what is said will not be revealed. For example, The doctor told her in confidence that her mother was terminally ill, or He told us in strict confidence that Gail was pregnant. This idiom was first recorded in 1632. Also see take into one's confidence.

Related Words

• clandestinely www.thesaurus.com
• covertly 
• furtively 
• personally 
• privately www.thesaurus.com
• quietly 
• stealthily 
• surreptitiously