Pearlash is potassium carbonate, a type of salt. The name pearlash is what it is called commercially because of its white granular or abstractly shaped particles.

Window glasses are made by mixing white sand, unpurified pearlash, and wood ashes. These materials are sifted, burnt, and placed in a mold to make window glass.

Quick breads (chemically leavened) which most zucchini bread recipes are, were not developed until the end of the 18th century. This took place in America, where pearlash was discovered. Pearlash is a refined form of potash, and it produces carbon dioxide gas in dough.

White salts, pearlash or salts of tartar are the common names. It was used as a leavening agent to make quick bread rise before baking powder was created.

The exact history of zucchini bread is not known but most quick breads were not developed until the 18th century after the discovery of the first leavening reagent 'pearlash'. And zucchini as we know it didn't exist until the 19th century where it was the result of a mutation of a squash plant (which did originate in the Americas) that occurred in Italy.