• unbeknownst •
ên-bi-nownst • Hear it!
Part of Speech: Adjective-Adverb
Meaning: Without the knowledge of, unawares.
Notes: If you want to, you may leave the ST off the end of this word and just say unbeknown, much like amongst and among. No one seems to know why the -st is even there. Beknown is the past participle of beknow "to acknowledge, admit knowledge of, to recognize", a verb rarely heard or read since the 16th century.
In Play: Unbeknownst is usually accompanied by the preposition to: "Ralph told the border guards that Manuela had sneaked into the trunk of his car unbeknownst to him." Remember, you can omit the final ST: "Unbeknown to the wedding guests, Harley Quinn had placed sardines on the engine of the bridal couple's getaway car."
Word History: All we have to do now is explain unbeknown. It is the past participle of obsolete beknow from Old English becnawan, negated: un-, negative prefix + be-, an intensifier + cnawan "to know". The English word comes from the PIE root gno-/gne- "to know". This same root produced Russian znat' "to know", Latin gnoscere "to know", as in cognitus "known, acknowledged", the origin of English incognito. Latin nobilis, which English borrowed from French as noble, was a reduction gnobilis, since the nobility was at one time thought to be more knowledgeable than others. The Greek descendant of the PIE word is visible in many English borrowings, too, such as agnostic, diagnosis, and prognosis.