rationalization (n.)
1825, "a rendering rational," from rationalize + -ation. Psychological use is from 1908.
Of the three works now on our table, the two which we have placed first have these laudable objects in view; an improvement on the former versions of the Psalms as compositions, and the rationalization, if we may so speak, of our Church psalmody. ["The British Critic," London, Jan.-June 1825]