If you are looking for where "hooray" came from, its etymology, would be in the 400s. Linguistics (the science of language and speech) starts at 401, and runs through American Sign Language books at 419.
As in the 900s (Geography), we take the same crazy path around the world for languages: 430s for German, 440s for French, 450s for Italian and several Eastern European, 460s for Spanish and Portuguese, 470s for Latin, 480s for Greek, and 490s for everything else (i.e. Apache, Russian, Egyptian hieroglyphics). Please remember, the 400s will house the dictionaries and how-to books for English speakers to learn, study, or translate these languages, but literature in these languages is found in the 800s (such as Don Quixote or The Odyssey). Why do Latin and Greek each get 10 places, while everything else is wedged into 490s? Because Melvil Dewey worked at one college's (Amherst) library and their curriculum, which focused heavily on Classics.
Some fun facts in the 400s: Simon Winchester (whom I have raved about before) has two books on the origin and history of the Oxford English Dictionary. If you, like me enjoy playing with words, Eats, Shoots & Leaves is also in this section.
Ruidoso Public Library has several types of Spanish dictionaries: European, Mexican, New Mexican and Southern Colorado, Latin American, street-wise, and medical, too! Our collections stretches as far as handwritten Japanese, Korean, Mayan glyphs, and Sanskrit.
Speaking of dictionaries, crossword puzzle dictionaries are not in the 400s; find them in the 793s, with the other puzzle books.