I believe that [nix meaning 'nichts' in german] is even intentional, the original author of nix (Eelco Dolstra) is from the Netherlands. The name comes from the fact that by default, nothing is available in build environments in nix.
Which is apparently confirmed by https://pdfs.semanticscholar.org/5fd8/8f89bd8738816e62808a1b7fb12d3ab14a2f.pdf but I can't access that.
Nix = slang for "nichts" = word for "nothing" in German