un·be·known \|ənbə̇|nōn, -bē|-\adjective orun·be·knownst\-ōnzt, -ōn(t)st\ Etymology:unbeknown from un- (I)+ obsolete English beknown known, familiar, from Middle English beknowen, past participle of beknowen to become acquainted with, from Old English becnāwan, from be- + cnāwan to know; unbeknownst irregular from unbeknown — more at know : happening without one's knowledge : unknown — usually used with to < two elderly women unbeknown to anybody — J.H.Holmes >