Definition of "stedfastly"

“He told Washington "that the Indians kept stedfastly attached to our interest.”

1754 April 22, Edward Ward, quotee, David A.Clary, George Washington's First War‎, Simon & Schuster, published 2011, page 77

… and having clearly perceived his duty, he has pursued it stedfastly in spite of opposition or adverse criticism.

1905, Booker T. Washington, “A Man About Whom the World Should Know”, in Independent