unbeknown
adjective /ˌʌnbɪˈnəʊn/
/ˌʌnbɪˈnəʊn/
(also less frequent unbeknownst
(formal) /ˌʌnbɪˈnəʊnst/
/ˌʌnbɪˈnəʊnst/
)- unbeknown to somebody without the person mentioned knowing
瞒着；背着 - Unbeknown to her they had organized a surprise party.
他们瞒着她筹备了一个给她意外惊喜的聚会。
词源mid 17th cent.: from un- ‘not’ + archaic beknown ‘known’. - Unbeknown to her they had organized a surprise party.