unbeknownst

Unbeknownst is an irregular variant of the older unbeknown, which derives from beknown, an obsolete synonym of known. But for a word with a straightforward history, unbeknownst and the now less common unbeknown have caused quite a stir among usage commentators. In spite of widespread use (including appearances in the writings of Charles Dickens, A. E. Housman, and E. B. White), the grammarian H. W. Fowler in 1926 categorized the two words as "out of use except in dialect or uneducated speech." The following year, G. P. Krapp called them "humorous, colloquial, and dialectal." Our evidence, however, shows that both words are standard even in formal prose.