I don't know--and I just spent quite a while on the Internet trying to find a reference that revealed the answer. I will suppose that it could be tied into the fact that the honey locust pods are edible and that bees enjoy the flowers, although the poisonous black locust has blossoms that are preferred by the bee, according to one site.

Maybe tsuwm or jheem will look in here and give us some insight about the etymology of the word 'locust'--tsuwm? jheem?