How does the latin word septentriones tell you how many stars make up the big dipper?

Given that in Latin, the word septem means seven, the word septentriones will tell us that seven stars make up the Big Dipper. 
And if you know anything about the Big Dipper, you will know that it is true - there are seven stars in this asterism. These seven stars are Dubhe, Merak, Phecda, Megrez, Alioth, Mizar, and Alkaid, and they are part of the constellation Ursa Major.

Just find a long word in the book.