Wiktionary
ni-vanuatu
n. Citizen of Vanuatu, regardless of specific ethnic group (but usually referring to native Melanesians)
Wikipedia
Ni-Vanuatu
Ni-Vanuatu is a demonym used to refer to all Melanesian ethnicities originating in Vanuatu. It also refers, more generally, to nationals and citizens of Vanuatu, whatever their ethnicity.
This recent coinage builds on the particle ni, which in some indigenous languages encodes the genitive, similar to the English ‘of’. Thus Ni-Vanuatu literally means ‘of Vanuatu’.
The term is mostly used in English and French, and is hardly used in Bislama, the country’s lingua franca, let alone in the indigenous languages of the archipelago.
NiVan is a commonly used abbreviation of Ni-Vanuatu.