King James Bible Dictionary

(Jeremiah 25:26), supposed to be equivalent to Babel (Babylon), according to a secret (cabalistic) mode of writing among the Jews of unknown antiquity, which consisted in substituting the last letter of the Hebrew alphabet for the first, the last but one for the second, and so on. Thus the letters sh, sh, ch become b, b, l, i.e., Babel. This is supposed to be confirmed by a reference to Jeremiah 51:41, where Sheshach and Babylon are in parallel clauses. There seems to be no reason to doubt that Babylon is here intended by this name. (See also Streane's Jeremiah, l.c.)

bag of flax or linen

A symbolic name, apparently applied to Babylon.
Jeremiah 25:26; Jeremiah 51:41

(from the goddess Shach , reduplicated) is a term which occurs only in (Jeremiah 25:26; 51:41) where it is evidently used as a synonym for either Babylon or Babylonia.