c.1500, "to make into one," from M.Fr. unifier (14c.), from L.L. unificare "make one," from L. uni- "one" (see uni-) + root of facere "to make" (see factitious). Unification is attested from 1851; the Unification Church was founded 1954 in Korea
The unifier of a set of expressions is a set of substitutions of terms for variables such that the expressions are all equal. See also most general unifier, unification. (1994-12-06)