What does "calabar" mean?

Calabar: A district on the west coast of Africa. Calabar bean, The of a climbing legumious plant (Physostigma venenosum), a native of tropical Africa. It is highly poisonous. It is used to produce contraction of the pupil of the eye; also in tetanus, neuralgia, and rheumatic diseases; -- called also ordeal bean, being used by the negroes in trials for witchcraft.