Meaning of 曰く in Japanese

Definition of 曰く

いわく(iwaku) 【曰く】

(n) pretext; history; past; story
(n-adv) according to ...; ... says
ふふ・・・いわくがあるのさ、あそこには。
He-heh... there's a tale behind that, for that place.

いわくつき(iwakutsuki) 【曰く付き ·いわく付き】

(n, adj-no) with an interesting history (story); with a shady history; with circumstances that are difficult to explain

いわくいいがたし(iwakuiigatashi) 【曰く言い難し】