some tlds don't allow two letter domain names. .de used to forbid two letter domains. (After a court order because of vw.de those restrictions were lifted, and

some tlds don't allow two letter domain names. .de used to forbid two letter domains. (After a court order because of vw.de those restrictions were lifted, and now there even exist one letter domains, though most of them are just squatted, for instance g.de which just redirects to p.de)