***DISCLAIMER***The following is not an exhaustive post. Instead, it makes a best effort to sufficiently answer the question.
Someone recently asked me about spells and, specifically, Latin spells. Furthermore, this person asked why they are so effective. Below is my response.
With respect to the question and yourself, spells are more than just a word; they are connected to spiritism. Deuteronomy clearly shows how God’s Word detests spiritism, as follows in Deuteronomy 18:9-14 (NASB):
9 “When you enter the land which the Lord your God gives you, you shall not learn to imitate the detestable things of those nations. 10 There shall not be found among you anyone who makes his son or his daughter pass through the fire, one who uses divination, one who practices witchcraft, or one who interprets omens, or a sorcerer, 11 or one who casts a spell, or a medium, or a spiritist, or one who calls up the dead. 12 For whoever does these things is detestable to the Lord; and because of these detestable things the Lord your God will drive them out before you. 13 You shall be blameless before the Lord your God. 14 For those nations, which you shall dispossess, listen to those who practice witchcraft and to diviners, but as for you, the Lord your God has not allowed you to do so.
Here, Moses clearly tells the Israelites about the clear abominations of the polytheistic Canaanites (verses 9-12). Among these activities include sorcery and the casting of spells (verses 10-11). Doing such a thing is detestable in God’s sight (verse 12). In fact, Carlson & Decker, in their book Fast Facts on False Teachings, cite the same text as they explain how sorcery (among other like items) falls under the umbrella of “Spiritist cults”, which are a type of cult that “spans the whole universe of darkness” (pp. 141-143). Darkness certainly is not a good thing (Ephesians 5:1-21; 1 Thessalonians 5; 1 John 1-2; Jude).
In considering why spells are powerful, one must consider no less than two things. One, this world is fallen because of the fall of man, specifically Adam and Eve (Genesis 2-3; see also Psalm 51:5). Romans 3:23 states, “for all have sinned and fallen short of the glory of God.” Sin has infected us all. This sin takes many forms. This includes but is not limited to sorcery and spell-casting. The second thing to consider is the current state of this world. Paul explains in 1 Timothy 4:1, “But the Spirit explicitly says that in latter times some will fall away from the faith, paying attention to deceitful spirits and doctrines of demons,” (see also Matthew 24; Mark 13:1-23; Acts 20:28-30; 2 Thessalonians 2). Given the plethora of false teachers that are in pulpits today and the popular forms of sorcery around the world, it is not surprising to see that spells in general would be powerful.
In considering why Latin spells specifically are still effective (I am thinking these spells are what the questioner meant, although I could be wrong), the aforementioned 1 Timothy 4:1 passage would apply to this. The popularity of so many sorcery-heavy things (Harry Potter, Dungeons & Dragons, Final Fantasy, QUIJA boards, tarot cards, etc.) combined with the fallen world we have makes them effective. Sadly, these types of things are starting to overflow into some churches. As a result, biblical ignorance represents another reason why these things are effective. Christians need to understand that God’s Word forbids this type of spiritism. They need to expose these deeds of darkness instead of view them as harmless (Ephesians 5). If more Christians did such a thing, perhaps the effectiveness of these spells (Latin and otherwise) would be diminished.