c.1200, "Not resembling," from un-
(1) "not" + like
. Cf. O.E. ungelic, O.Fris. unlik, O.N. ulikr, M.Da. ulige. Unlikely "not likely to occur" is attested from late 14c. (cf. O.N. ulikligr, M.Da. uligelig). Meaning "not likely to be true" is recorded from 1590s.