Locust tree can mean:

• Any of a number of tree species in the genera Gleditsia or Robinia, including:

Honey locust (Gleditsia triacanthos), a leguminous tree with pods having a sweet, edible pulp

Black locust (Robinia pseudoacacia), a leguminous tree with toxic pods

Water locust (Gleditsia aquatica), a leguminous tree with one seed per pod

• Or less commonly, "African locust bean tree" (Parkia biglobosa), which is also known as néré
• Also not commonly, the carob tree, Ceratonia siliqua, whose pods are called locust beans.

Etymology

"Locust" comes from the Latin locusta, meaning both "locust" (the insect) and "lobster". By analogy with a levantine use of the Greek word for the insect, akris, for the pods of the carob tree which supposedly resembled it, the pod-bearing North American tree was called "locust" starting in the 1630s.^[1]

References