These are the local fruits called Mahuluhulu - you try saying it! They go by many different African names, but the only English one I've heard is monkey orange. The outer shell is very hard; I have seen it used in crafts, but never knew the fruit was edible. Now they are green, and can be cooked in porridge, but will soon turn yellow, ripe and sweet, ready to eat.
In the video below, Prisca explains their use, and gives me a pronunciation lesson.