A strong-smelling substance secreted by beaver glands, historically used in medicine, perfumery, and as a food flavoring.
From Latin castoreum, from castor (beaver). The Romans knew of this substance and valued it highly. The word entered English through Latin scientific terminology in the Middle Ages.
Castoreum is still approved as a 'natural flavoring' in the FDA—it's been used in vanilla ice cream and other foods for centuries! Beavers produce it to mark territory, but humans found it smells like vanilla, leather, and something animalic.
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