Sooth·fast a. Firmly fixed in, or founded upon, the thruth; true; genuine; real; also, truthful; faithful. [Archaic] -- Sooth*fast*ness, n. [Archaic] “In very soothfastness.”
Why do not you . . . bear leal and soothfast evidence in her behalf, as ye may with a clear conscience! --Sir W. Scott.
Sooth·fast, adv. Soothly; really; in fact. [Archaic]
I care not if the pomps you show
Be what they soothfast appear. --Emerson.