https://learn.microsoft.com/en-us/dotnet/api/system.globalization.cultureandregioninfobuilder.regionnativename?view=netframework-4.7.2
CultureAndRegionInfoBuilder.RegionNativeName Property (System.Globalization) | Microsoft Learn
Gets or sets the full name of the country/region as known by the people of this custom culture.
property systemglobalizationmicrosoftlearn