Where did Castile soap originate?

Castile soap is an olive-oil-based hard soap made in a style similar to that originating in the Castile region of Spain. The origins of Castile soap go back to the Levant, where Aleppo (Syrian) soap-makers have made hard soaps based on olive and laurel oil.

It is commonly believed that the Crusaders brought Aleppo soap back to Europe in the 11th century, based on the claim that the earliest soap made in Europe was just after the Crusades.

In the 17th century, the soap caused controversy in England, since it supplanted the unnamed local soap after the Spanish Catholic manufacturers purchased the monopoly on soap from the cash-strapped Carolinian government..

The sale of a monopoly in Protestant England to a Catholic company caused great uproar, ending with the Castile soap company eventually being stripped of the monopoly.