The Ionite Nebula was a nebula located near Luria. Few Lurians traveled far from it.
In 2372, Drex, son of Martok, asked Morn why he was so far away from the nebula. (DS9: "The Way of the Warrior")
Drex's line about the Ionite Nebula was not mentioned in the script of the episode and may have been added later.