Some domain names may be permanently or temporarily reserved or restricted for registry operations, as premium domain names or to comply with ICANN requirements.
To comply with ICANN requirements, all two-character domains shall be initially reserved, however may be released in the future. In addition reserved names for a) International Olympic Committee, b) International Red Cross and Red Crescent Movement, and c) Intergovernmental Organizations, for new gTLDs., are not available in accordance with ICANN. The list of these names can be found here.