Source : Webster's Revised Unabridged Dictionary (1913)

Soothfast \Sooth"fast`\, a. [Sooth + fast, that is, fast or firm
   with respect to truth.]
   Firmly fixed in, or founded upon, the thruth; true; genuine;
   real; also, truthful; faithful. [Archaic] --
   {Sooth"fast`ness}, n. [Archaic] ``In very soothfastness.''
   --Chaucer.

         Why do not you . . . bear leal and soothfast evidence
         in her behalf, as ye may with a clear conscience! --Sir
                                                  W. Scott.

Soothfast \Sooth"fast`\, adv.
   Soothly; really; in fact. [Archaic]

         I care not if the pomps you show Be what they soothfast
         appear.                                  --Emerson.