Ok, at first, you need the history of Lorraine.
In the first time of the duchy (869-1200), there is two different languages: Lorrain Roman ( Langue d'Oïl, french familly group) and Francique ( Mosel Frankish / Lothrìngerplatt, one of the first german language speaked by the Franks ), but it's one same culture ( but some difference with far west and south of the duchy, like Vosges). After 1250-1300, the duchy is divided in two bailly, Loherraine (Roman) and "Allemagne"(Francique), but the second is now reduce by 50%, so all the countys in the north east.
Lorraine is border by France and burgundy in west and south west, imperial county of burgundy ( Franche-comté) in south, Luxembourg, Tier and Palatinate in north ans the Alsace, Decapolis and Habsbourg territory in east.
I don't know how do you translate "Lorrain" in english, Lorrainian ? in some historical games/mod, that word is don't translate.
What do you need exactly for the Lorraine in the mod ?
Heraldy ?
General names ?
specific unit name ?
tell me all what you need, i'm here for you.
( sorry for my really bad english
)