wythe

Etymology
Uncertain. The chimney-partition sense may derive from the fact that a single wythe or thickness of brick has often been used for such partitions.
 * Perhaps an alteration of.
 * Perhaps related to, from.

Noun

 * 1)  A continuous vertical section of masonry, one unit in thickness.
 * That wall has to be at least three wythes of brick to support your load.
 * 1)  A partition between flues in a chimney.