Complex sentence: The terms "Salish" and "Salishan" are used interchangeably by linguists and anthropologists studying Salishan but this is confusing in regular English usage, because the name "Salish" or "Selisch" is the endonym of the Flathead Nation.
Split into simpler sentences: The terms "Salish" and "Salishan" are used interchangeably by linguists and anthropologists studying Salishan, but this is confusing in regular English usage. The name "Salish" or "Selisch" is the endonym of the Flathead Nation.