Page 201. " Lumos! And a tiny light appeared at the end of it "

Although Harry and his friends do not seem to learn any foreign languages at Hogwarts, they often use Latin. Almost all the curses, spells and charms derive from Latin words. The charm ‘Lumos’ for example, which causes a light to appear at the end of the wand, means ‘light’ in Latin; ‘Nox’, the command given to extinguish this light, means ‘darkness’.

Even two of the three forbidden curses are in Latin: Crucio, a curse which causes pain, in Latin means ‘torture’; Imperio, which makes the victim do whatever the curser wants, in Latin means ‘command’.

This ‘dead’ language is used in many ways throughout the seven Harry Potter books. Hogwarts’ motto “Draco Dormiens Nunquam Titillandus” is Latin for Never Tickle A Sleeping Dragon.

Latin was once a very widely spoken and important language. When the Romans conquered almost all Europe, Latin was a common language across the Empire. Scholars used to study it at school, thus almost all books were written in this language. It was also the main language of Christianity.

Modern ‘romance’ languages like Spanish, Italian and French, are descendants of Latin, whilst other European languages have acquired many words from it. More than 30% of English words have Latin roots.

Page 215. " There is none more curious or more deadly than the Basilisk "

Basilisks have been a part of European mythology for thousands of years.  They come in different forms, some resembling snakes and others closer to cockerels.  They are said to be born from the egg of a toad, hatched by a cockerel.  Other serpents flee for safety when they hear the first ‘hiss’ of a basilisk, even if they are in the middle of a meal.

In mythology there are different versions of how the basilisk kills. Some say that this King of Serpents burns everything it touches, others that its breath poisons the air.  Still others claim its blood is so potent that if a knight drives a spear through it the poison will kill not only the knight but also the horse he is riding. Some believe that a basilisk, like the Medusa, is capable of turning anyone who looks into its eyes to stone. 

Supposedly a basilisk can be killed by the crow of a cockerel, or by holding a mirror up to its "baleful gaze".  Travellers in the Middle Ages were said to carry cockerels with them as protection against basilisks.