In English, null means nothing, nil, empty or void. In computing, null is a special value for nothing, an empty value. In geography, null tends to be what you get when you've been unable to geocode a place or an address and haven't checked the geocoder's response. What you end up with is a pair of coordinates of 0 degrees longitude and 0 degrees latitude, a point somewhere in the middle of the Atlantic Ocean, south of Ghana and west of Gabon. It's here that you'll also find Null Island, if you look hard enough.

The website for the Republic of Null Island (like no place on earth) says this about the island's location ...

The Republic of Null Island is one of the smallest and least-visited nations on Earth. Situated where the Prime Meridian crosses the Equator, Null Island sits 1600 kilometres off the western coast of Africa.

... but Null Island is an in joke created by Nate Kelso and Tom Patterson as part of the Natural Earth data set in January 2011.