What is "quassia amara"

Quassia \Quas"si*a\, n. [NL. From the name of a negro, Quassy, or Quash, who prescribed this article as a specific.] The wood of several tropical American trees of the order Simarube[ae], as Quassia amara, Picr[ae]na excelsa, and Simaruba amara. It is intensely bitter, and is used in medicine and sometimes as a substitute for hops in making beer.

Quassia amara (amargo, bitter-ash, bitter-wood) is a species in the genus Quassia, with some botanists treating it as the sole species in the genus. The genus was named by Carl Linnaeus who named it after the first botanist to describe it: the Surinamese freedman Graman Quassi. Q. amara is used as insecticide, in traditional medicine and as additive in the food industry.