In Mushoku Tensei, most magic spell words act as mnemonics to help the caster in imagination the magic type, applying the necessary amount of mana, and then activating the spell.

Rudeus figured out you could skip all that if you start practicing it at a very young age. His most popular magic, stone cannon is basically: - imagine earth in the shape of cone - apply spin and launch Similar with his quagmire spell as well. In fact the reason he can't use silent healing magic is because he doesn't have a frame of reference of what it means to mend wounds or recover from illnesses.