Why Latin?
(Or any dead language) for reciting spells and rituals?
Well, let's say that someone who writes spells is called a spell master, and people who use them are spell casters. Spell masters, if not of latin origin, would of course write their spells in their own language first to empower it's connection. Maybe a spell would say, "Strenghten my mind, and from air, let me produce fire!" and after feeling strongly for that sentence, the spell master would create fire! But what if it's just my everyday life and I need to use this same exact sentence to piss off my neighbor for internal joke's sake? What if I accidentally felt strongly to the sentence and put him on fire? Human mind is tricky afterall, and words are the strongest connections to thoughts.
The best solution is to rewrite and restudy the spells in a different language. Now, you won't accidentally cast a spell. But how about the future spell casters who would study your book? It has to be a language that people of any walks of life don't use casually. Enter: Latin, Welsh, etc.
And that's why Spell Masters usually use Latin.
