Southern magic

Southern magic was a term used to describe unique spells written in a different magical language.

Origins
As the named implied, southern magic originated in south Faerûn, specifically Halruaa. Wizards who were not native Halruaans could not read spells or scrolls written in the southern magic language, even through the use of a read magic spell.

Rumors and Legends
In the mid 1360's DR, the brilliant wizard Random Riellor successfully created a spell that allowed non-Halruaans to decipher a spell written in southern magic. This spell was called read southern magic.