What does NGN stand for?

Nagano - Japan - Seismograph station code, US Geological Survey (SEIS)

Nargana - Panama - Airport symbol (OAG)

National Geographic Names Data Base - Geological Survey - Database

Negotiation - Telegraphy (PCTE)

News Group Newspapers - British

Ngwo - Language code (ETLW)

NRG Resources Ltd. - Vancouver Stock Exchange symbol