Teachers can build on students' familiarity with and respect for the Harry Potter books to create source-based vocabulary lessons. The idea is to work with the Latin roots that J. K. Rowling uses to create original names for places, people, and magical charms and then to extend students' knowledge through exploration of additional English words based on the same roots. Besides being an efficient way to teach vocabulary words in a meaningful context, the approach helps students see that when new words are needed, they are often based on old, familiar words. It also trains students to look for metaphorical and other associations while developing confidence in their ability to make "intelligent guesses" about words they do not know. Various Latin roots are discussed, along with many words derived from them. Teachers can focus in a day's lesson on one root and several derivatives whose meanings will reinforce one another. (Contains 1 figure and 2 tables.)