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The etymology of Harry Potter spells

Every spell has a story to tell…

Hermione holding up her wand from the Chamber of Secrets
Harry Potter and the Chamber of Secrets

Harry Potter is a world of strange and magical language, filled with words that sound alien and new, but in fact have their roots in the real-world. Spells are no exception, with the origins of many incantations harking back to Latin terms and phrases; some spells translate pretty directly, while others have been carefully crafted and assembled from fragments of other languages. It's a fascinating example of how language changes and evolves, so here's a look at five of our favourite stories behind some of the wizarding world's most famous spells…

The Patronus Charm

'Expecto Patronum', the spell that conjures up Harry’s magnificent stag Patronus, roughly translates into 'I expect (or 'await') a guardian' in Latin, which is apt. The actual result of the spell, the Patronus itself, has an even more interesting history. In Ancient Rome, the word 'patronus' meant protector too, but with very different connotations. A patronus in Ancient Rome was someone of a high class who had a 'patronage' relationship with a client, who would usually be less rich, or lower class. In turn, the word ’patronage’ most likely came from the term 'Pater', which means 'father' in Latin. In whatever time, in whatever form, the word 'patronus' always relates to protection.

Harry casts his Patronus while in disguise at the Minstry.
© JKR/Pottermore Ltd. ™ Warner Bros.

Petrificus Totalus

The Body-Binding spell is heavily influenced by Latin, as you may have guessed from its very Latin-sounding name. However, there are dashes of Ancient Greek in this incantation too. First, we have 'Petra', which is derived from 'petros' which means 'rock' in Greek. 'Ficus' is a Latin suffix which denotes 'making' or 'doing' something. ‘Totalus’ is a loose reworking of 'totalis', which, once again, is Latin, meaning 'total' or 'entire'. So roughly speaking, ‘Petrificus Totalus’ translates to 'Make rock totally’, which we're sure victims of the curse, such as Neville Longbottom, totally understand all too well.

Neville falls victim to Hermione's Petrificus Totalus spell
Harry Potter and the Philosopher’s Stone

Expelliarmus

Expelliarmus is one of the most-used spells across all seven Harry Potter books, to the extent that Harry is known by the Death Eaters for using it during Deathly Hallows. We've seen the word so many times, but how did it come together? ‘Expel’ harks back to 1300s Middle English, where two Latin terms were combined to create it. 'Ex' means 'out' and 'pellere' means 'to drive', which finally formed the word ‘expel’. Its definition in basic terms means to 'drive out'. 'Armus', as you may expect, is indeed Latin for a similar sounding part of the body: the arm, or specifically the shoulder joint. In time, the term 'arm' took on combat meaning (such as, to 'arm' yourself with a wand) with the Latin term 'arma' meaning weapon. Piecing the syllables back together, we have a rough translation of the phrase 'drive out weapon' – which is precisely what Expelliarmus does.

Lord Voldemort is killed by his own rebounding spell in a battle against Harry in the great hall from the Deathly Hallows.
© JKR/Pottermore Ltd. ™ Warner Bros.

Lumos and Nox

Sister spells Lumos and Nox give light and take it away, respectively. Lumos could well come from the 19th-century Latin word ‘lumen’, which simply means 'light'. Adding the Latin suffix 'os' means to 'have something’: to have light, in this instance. Nox is Latin for 'night', but is also rooted in Greek mythology. 'Nyx', closely related to 'Nox', is the name for the Greek goddess of night: a feared, shadowy figure who was known as a powerful force, and even intimidated the mighty Zeus.

Dumbledore and Harry use Lumos inside the Horcrux cave
Harry Potter and the Half-Blood Prince

Sectumsempra

A word dominated by the letter S was related to a man with a similar example of sibilance in his own name – Mr Severus Snape. But surely Snape must have had more inspiration than that for such a complex spell name with such deadly intentions? Digging deeper, we can see that Snape was fond of Latin too, seeing as the first half of his self-made curse, 'sectum', is Latin for 'having been cut’: an interesting choice for a man who has the word 'sever' in his own name.

The second part of the word, however, is fascinating. Because although 'sempra' isn't a Latin word, it is very close to the word 'semper', which was known in the Latin phrase 'semper fidelis'. This becomes a particularly big deal once you realise what it means: ‘always loyal’. Pretty perfect, don't you think?

Snape telling Harry to be quiet at the Tallest Tower
Harry Potter and the Half-Blood Prince