Slow or Stop Movement? Solo Prodigal Learner

Of all the second year charms, Jack had kept the Slowing Charm for last because he had original considered it vastly inferior to the Freezing Charm, 'Immobulus'. It had been difficult for him to think of what circumstance would make slowing something more effective than stopping it. If liquid were to spill or someone was in pursuit, it only made sense to want to stop their movements instead of slowing them.

However, as Jack read more about how the Slowing Charm was invented and how it had been used to save the lives of many falling wizards in the past, including Harry Potter, the true value of the spell became more apparent to the Slytherin. Even after he learned how the charm could be useful, though, it continued to give him trouble as he did his best to study more about it.

For one thing, the incantation was 'Arresto Momentum'. "Ah-REST-oh mo-MEN-tum," he spoke aloud, enunciating each syllable with exaggeration to make sure he got used to pronouncing it correctly. As he did so, however, he realized that the word 'momentum' was, as far as he knew, a proper English word despite the fact that most spell incantations seemed to be Latin or at least derived from Latin. So what was an English word doing in there?

If he tried to translate the incantation from Latin to English, he was pretty sure that made it into 'arrest moment' and double-checked this to make sure it was true. Even that had its problems, though, because it implied 'arresting' a moment. Scratching his head in confusion, the Slytherin first year quickly went to look up a book of Latin root words and etymology.

The etymology of the word 'arrest' described it as a late Middle English word derived from the Old French word 'arester' which was based on the Latin prefix 'ad-' or 'at, to' and the Latin suffix 'restare' or 'remain, stop'. So, essentially, 'arrest' was the synonym for 'to stop' or 'stop' as a verb. And that wasn't all.

Apparently, 'movement', 'moment', and 'momentum' all came from the same family of Latin words. The Latin word 'movimentum' had eventually evolved into the Latin 'movere' from which the late Middle English 'movement', the late Middle English 'moment', and the late 17th century 'momentum' had all been derived.

As much sense as that made in terms of momentum relating to movement through space within a certain amount of time, or a 'moment', the spell didn't seemed to really have anything to do with any of that. While the incantation itself made Jack think on impulse that it 'arrested' or 'stopped' momentum, the term 'momentum' in English meant speed multiplied by mass, which equaled force. So if momentum was force, the spell wasn't so much focusing on slowing the force of something as it was on the speed unless it was affecting the force indirectly.

So why couldn't they have made it translate to something like 'slow speed' or 'slow velocity' in Latin rather than 'stop movement' or 'stop momentum'?

Speed was the rate at which an object covered distance. Velocity was similar, but the rate at which an object covered distance in terms of position; it was direction-aware. Jack supposed that in this case, either term would work better than what already existed, so he searched up the Latin roots and etymology for each.

The term 'velocity' was apparently a late Middle English word. It seemed to trace its roots back to either the Latin term, 'velocitas' or the French term, 'vélocité' (the latter of which may have also been derived from the former). Regardless, those terms were derived from the root word 'velox' and possibly the prefix, 'veloc-', both of which meant 'swift'. The problem with this was that Jack had been referring to velocity as a measurable rate, not a describing adjective, so that meant 'velocity' in any form was likely to be useless for his purposes.

Turning instead to the term 'speed', he was only able to trace it back to Old English and Germanic roots with meanings of 'prosper' and 'succeed' which were also not what Jack was looking for as, aside from not being Latin, they were verbs rather than a rate.

He supposed there could be no Latin equivalent for the English momentum if it was supposedly already considered a Latin term, but what about 'movimentum', a more ancient Latin term from which 'momentum' had been derived? Wasn't that a Latin word more closely-related to 'movement' than 'momentum'? Even 'motus' as a translation for the English 'motion' seemed to make more sense.

That aside, 'slow' could have been translated to 'tardus' - an adjective - or 'tarde' - an adverb. Thus, wouldn't an incantation like 'Tardus Movimentum' or 'Tarde Movimentum' made more sense for a Slowing Charm meant to slow movement than 'Arresto Momentum' which could have meant 'stop movement' or 'stop moment'?

Upon reading more into the possible etymology behind the incantation of the spell itself, Jack discovered that the author of that article believed that the 'Arresto' part came from the Anglo-French term, 'arester' meaning 'to bring to a stop' (with no mention of the Latin prefix and suffix 'ad-' + 'restare' to make the Latin 'adrestare'). That lack of explanation regarding the Latin roots made Jack doubtful about the author in itself, but then there was more.

The article claimed that the 'Momentum' part of the incantation simply came from the Latin term, 'momentum' (disregarding its roots from the Latin words 'movimentum' and 'movere' completely) and that it meant 'the force or strength gained whilst moving' which Jack was fairly certain was the English definition of the term, not the Latin one (if it even was considered a true Latin term at all rather than simply derived from Latin).

At the very end, the author claimed that the literal translation of the spell's incantation, 'Arresto Momentum', meant 'bring its momentum to a stop'. In other words, 'stop momentum' - aka, what the first year had translated the term into as English words in the first place.

Regardless of the many issues Jack had with the article and the author who had written it, he had hoped that it would have at least come to a better explanation as to why the terms chosen for the incantation were what they were, but the final conclusion was no better than his own deductions. The incantation simply made little to no sense in relation to what it was expected to do when performed as a spell.

Well, whatever; he wasn't the one in charge of inventing spells and it wasn't like he had the power to change it even if he'd wanted to, anyway. He just found himself wishing once again that, like with the Revealing Charms, Concealment Charms, and Concealing Charms, the wizards and witches who had invented said spells had thought to put more consideration into the technicalities and nuances of the English (and, in this case, Latin) languages.

All he had to do, though, Jack reminded himself, was perform the actual spell. Tossing an apple from lunch high into the air of the classroom, the boy aimed his wand at it and cried, "Arresto Momentum!" with the wand-waving motion of a capital 'M' as the fruit began to drop.

Though there was no visible light as there was with many other charms and spells, Jack kept his wand and focus trained on the apple until he noticed it begin to slow. It didn't slow by much, however, and hit a desk and then the floor with a thud. Hurrying over to fetch it before it rolled away, the redhead threw it up into the air to practice the spell once more.

Several tries and a very bruised apple later, Jack washed off the fruit and went to sit somewhere to eat it, contemplating the mechanics of the spell still. He wondered if it might have originally been an attempt to stop movement rather than slow it and simply found another use in its failed effect. Regardless, the first year resolved to practice more and more until he could slow the apple's movement to a significant degree so that it was nearly stopped. Then, he decided, he would move on to practicing on something more difficult, like water.

As he bit into the apple, however, the Slytherin rewarded his day's efforts with a snack and some rest. At least he had learned the basics on which to found a better understanding and mastery of the spell over time.