What is the byproduct of bitter olive oil called?

The byproduct of bitter olive oil is known as amurca. This term refers specifically to the residue left over after olive oil has been extracted from the olives, particularly when they are of a bitter variety. Amurca was historically used in various contexts, including as a fertilizer, animal feed, and sometimes even for medicinal purposes.

The other terms can be understood in their respective contexts: oleum refers generally to oil in Latin and does not specifically apply to the byproduct; vinum means wine and relates to fermented grape products; mulsum is a mixture of wine and honey, which is not connected to olive oil production. Understanding these distinctions helps clarify why amurca is the appropriate answer related to olive oil byproducts.