Whether you're a wizard, squib, or just plain muggle, you're probably celebrating the Chosen One's birthday today. And what better way to do it than by examining the origins of some of the wonderful words J.K. Rowling used to create the world of the Boy Who Lived?
Rowling studied Latin at the University of Exeter, and she clearly got a lot of use out of that study time: Most of Harry Potter's spells have their roots in classical Latin. Harry's signature spell, Expelliarmus, is used to disarm an opponent, and, according to the Oxford English Dictionary, combines the Latin expellere, "to drive or force out," with arma, which means weapon. The summoning charm Accio is Latin for "I summon." And Expecto Patronum, which wizards use to create an animal that drives away Dementors, translates to "I wait/hope for a patron."
The author also repurposed regular words to suit her needs to rather delightful ends. According to Wordnik, dumbledore is an 18th century English word for a bumblebee. ("Because Albus Dumbledore is very fond of music, I always imagined him as sort of humming to himself a lot," Rowling once explained.) And to name the wizarding world's most obnoxious thief, Rowling used the word Mundungus, which means "waste animal product; organic matter unfit for consumption" or "poor-quality tobacco with a foul, rancid, or putrid smell."
These are just a few examples of excellent Harry Potter word origins. For more, head over to Wordnik.