Interesting, that Arakawa has said she based the Ishbalan characters more or less on the Ainu of Japan, and their persecution. Watching the History Channel today, I heard a repetitive name come up -
Ishbaal, who fought against David.
I wouldn't be surprised if that's where Arakawa got the name for her people, considering her other historical researches into that time period and names for other races/countries in her world.