Dunder / Backset??
Can some one explain the difference between DUNDER and BACKSET.




Dunder, a term unfamiliar to
the ear of a European distiller, is the lies or feculencies
of former distillations, serving all the purposes of yeast
in the fermentation. It is derived from a Spanish word,
redunder, the same as redundans in Latin, and is well
known among the planters in the West Indies. The
attennating properties of this ferment are such, that
the materials with which it is mixed are said to yield
a much greater proportion of spirit than could be obtained
if they were fermented without it: it serves the
same purpose as jalap mixed with molasses, which has
been sometimes employed in Great Britain for cutting
down the frothy head at the close of fermentation;
and it is nsually preserved from one year to another
for this purpose, in such large quantities as to fill most
of the backs or fermenting tuns. Dunder soon becomes
covered with so thick a film as to exclude the air, and
the sediment leaves the intermediate fluid pure, of a
bright amber color, which, when carefully drawn off,
is employed as already described, in proportions suited
to the nature of the fermentation; to this dunder may
be attributed the best flavor of the rum.
Source: Muspratt, Sheridan; Horsford, Eben Norton (1860). "Chemistry, Theoretical, Practical, and Analytical: As Applied and Relating to the Arts and Manufactures". p. 107.