@Tes yeux noirs,
Quote:Unbeknownst is more common in British English than elsewhere, but even there it is very old fashioned, bordering on archaic. Also excessively 'wordy'. I suggest using 'unknown'., rewriting if necessary.
Not at all good advice, Tyn.
M-W
unbeknownst
adjective un·be·knownst \ ˌən-bi-ˈnōn(t)st \
variants: or less commonly unbeknown play \ˌən-bi-ˈnōn\
Popularity: Top 10% of words