카더라

Etymology
The noun sense is derived from the verb, originally in the construction.

A January 1980 opinion editorial, published in the  daily, states that the noun was at that point a neologism that had only recently begun circulating in the Gyeongsang dialect-speaking city of Daegu, in reference to the unsubstantiated political rumors following the chaos of the, 1979.

Verb

 * 1)  they say, it is said;

Noun

 * 1)  an unsubstantiated rumor, now especially one on the Internet