Sheshach
   (Jer. 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 Jer. 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 Streane's Jeremiah,
   l.c.)
   

Sheshach, bag of flax or linen