Warthogs (Phacochoerus africanus) are called thus because of the wart-like protuberances on their faces that really consist of bone and cartilage. You might like to look at them more closely the next time you get an opportunity to see them and note that the boar has two pairs (which they use for defense when fighting as these provide a cushion to the blows from the tusks of their opponent) while the sow sports only one pair of ‘warts’.
I was looking through a list of collective nouns recently and wonder if you already know that a group of warthogs is called a sounder of warthogs. As female warthogs tend to live in matriarchal groups, usually consisting of one or two adult females and their young, they ought to be called sounders. I have been unable to discover why this particular word is used.
Apart from the apparent facial warts, warthogs also sport white facial crests which, in the right light and angle, look a bit like tusks. The role of these is to make the animals look a lot fiercer than they are when threatened.