Proper noun
Neustria
(historical) The western part of the Frankish empire, corresponding roughly to modern-day northern France.
Columbanus made his way across Gaul to visit King Chlothar II of Neustria at Soissons where he was gladly received. Source: Internet
However, a Germanic language was spoken as a second tongue by public officials in western Austrasia and Neustria as late as the 850s. Source: Internet