Yisrael Saba versus Yisrael Zuta:
In Kabala we find two concepts of the name Yisrael. One is called the Old Yisrael, or Yisrael Saba, and the second is called the small Yisrael, or Yisrael Zuta. Yisrael Saba refers to the level of Nehiy of Chochma of Atzilus as it descends into the Midos. In other words, it is the level of of Midos that are found within Chochma. This is because the term Yisrael refers to Chochma, as Yisrael is a make up of two words, Yisra Keil, anmd the name Keil refers to Chochmah. Saba refers to light and hence Yisrael Saba means the light of Chochma as it shines in the Midos. On the other hand, Yisrael Zuta refers to the level of Chochma found in the Midos itself. This level of Chochma does not derive from Chochma of Atzilus but is rather completely incorporated from within the Midos of Z”a.
 Siddur Im Dach p. 11b