It helps disambiguate Nixlang from the codebase that includes the Nix CLI and the Nix daemon, for one. It's also an unambiguous designation for the original Nix implementation, as opposed to Lix and Tvix.
A Lix user might well reasonably say they 'use Nix' because they use Nixlang. Thus some people are Nix users but not CppNix users. As Tvix matures, the same will be true of Tvix users.
Because apparently nix isn’t enough despite being the project name, executable name, and the name of the language it implements. No one calls rust “rustrust”
Full caps AWK feels like a relic from the screaming UNIX days, and golang for Go is incredibly common (and as far as I can tell, the proximate cause of the nixlang term)
https://news.ycombinator.com/item?id=41503923