unknown or unperceived; without one's knowledge: usually with to
Without the knowledge of a specified party. Used with to: Our cousin had been ill for years, unbeknownst to the family.
Origin of unbeknownstunbeknown + -st (as in amongst).
- (followed by to) without the knowledge of
- He went home early, unbeknownst to his mother.
C. 1636: unusual form of un- +"Ž beknownWOTD - 23 June 2012