How did Brian come up with the name of the berries in Hatchet?

Brian researched the different kinds of berries and animals when he got home after his rescue.

There were many questions in his mind about what he had seen and known, and he worked at research when he got back, identifying the game and berries. Gut cherries were termed choke cherries, and made good jelly. The nut bushes where the foolbirds hid were hazelnut bushes.