Ferrothorn is a Pokémon resembling a flattened durian. Its metallic body is covered in thorns, with three black stripes circling its width, the middle stripe having triangular decorations below the eyes of Ferrothorn. Its eyes have green rims, yellow scleras, and dark pupils. There is a green spike at the top of its body, and extending around it are vine-like, long green appendages tipped with spiky metal disks. It can use these appendages to either cling to ceilings of its cave or walk around. When hanging, it can attack its prey underneath by shooting spikes.
Ferrothorn is the only Pokémon with a base stat total of 489.
It appears to be based on durian plants. Its vines resemble military flails. The vines also resemble a fully-grown brier plant, just as its unevolved form resembles a seed. It could also be based on the tribulus, which is a species of thorny plants whose name, during Roman times, also meant caltrops, which is a thorny metallic weapon used to puncture the feet of invading soldiers. Also, the "tri-" in tribulus means "three", which is also the same number of pods Ferrothorn has.
Ferrothorn is a combination of "ferrous" (meaning contains iron) and thorn (a protective spine found on many plants).
Nutrey may be a combination of nut and rey (Spanish for king), 鈴 rei (bell), or trey (Italian for three anglicized, referring to its three appendages).