c. 1600, "allowing to pass through," from Medieval Latin *permissivus, from Latin permiss-, past-participle stem of permittere "to let go, let pass, let loose" (see permit (v.)). In sense of "tolerant, liberal" it is attested by 1946; by 1966 it had definite overtones of sexual freedom. Earlier it meant "permitted, allowed" (mid-15c.). Related: Permissively; permissiveness.
updated on April 12, 2020