undoubtably

From Middle English undoutably, equivalent to undoubtable +‎ -ly.

undoubtably (not comparable)

1. (sometimes considered nonstandard) Without doubt; indubitably, undoubtedly.
   • 1679, Edmund Everard, Discourses on the present state of the Protestant princes of Europe, Dorman Newman, London, p. 20:

     I leave it to all the Protestant Princes of Europe to judge if their safety can be solidly established in their Leagues and Confederations with the Princes of the Roman Communion, as it may be undoubtably effected by their Leagues and Confederations amongst themselves.

   • 1887, Albert Parsons, Autobiography:

     This method would undoubtably strike a wholesome terror into the hearts of the working classes.

   • 1963, Charles Poore, "Books of The Times: The Curtain Speeches of Somerset Maugham," New York Times, 5 Oct., p. 18:

     Maugham suggests that storytelling began when primeval hunters told tales around their fires and turbaned raconteurs held forth in what Sinclair Lewis called the clattering bright bazaars. He's undoubtably right.

   • 2003, M. Van Atten and J. Kennedy, "On the Philosophical Development of Kurt Gödel," The Bulletin of Symbolic Logic, vol. 9, no. 4, p. 431:

     Thus, by analogy, philosophical propositions will involve primitive terms, to be arrived at, undoubtably, by a kind of conceptual analysis.

• "Undoubtably" is considered to be nonstandard English by some authorities (for example, Garner's Modern American Usage (2009)), and the term is seldom found in modern literary writing.[1] The Oxford English Dictionary provides no examples of usage after 1513 and characterizes "undoubtably" as "? Obs.," wondering whether the term is obsolete.[2] Nevertheless, many examples of its usage can be found in 20th- and 21st-century popular English and in contemporary academic journals.

• indubitably, undoubtedly, doubtlessly, unquestionably