also re-unify, 1879, from re- + unify. Related: Reunified; reunifying.
c.1500, "to make into one," from Middle French unifier (14c.), from Late Latin unificare "make one," from Latin uni- "one" (see uni-) + root of facere "to make" (see factitious). Related: Unified; unifying. Unified (field) theory in physics is recorded from 1935.