The phrase "yada yada" is attested in English beginning in the 1960s and carries the sense of "and so on", with a derogatory sense of continuing meaningless empty chatter. In other words, you might say "She was describing how much her shoes cost, and where she bought her jacket and yada yada" but not "The doctor explained to me treatment options for my cancer and yada yada". The origin of the word is actually uncertain.
While some dictionaries derive it from the Hebrew "yada" (knowledge) due to its sound, an etymological connection would also require similarity in meaning as well, which is not present. Another proposed etymology is from the obsolete English word "yatter", which is closer in meaning. However, both suggestions are ultimately speculative.