Where Do Words Come From?

My class and I have been reading Pippi in the South Seas, one of my favorite books from childhood. In the third chapter, Pippi finds a Spink, Pippi makes up her own words and wonders who decided that we should call a tub a tub, a table a table, and so forth. So, I stop and ask the kids to think about the earliest people in the world, and where do they think our language came from. Well, Marina and William start having a heated argument about this. William thinks that our words came from the early Egyptians. Not to be out done, Marina shouts out, "Nuh-uh, William! Don't you know that the first person on Earth was Adam Smith!"