Development of 'landlocked' sites behind existing buildings, such as rear gardens and private open space, usually within predominantly residential areas. Such sites often have no street frontages.
Pictures of backland housing in Glasgow
There are other pictures and maps with the tags backlands and backcourt
"Land behind or beyond an area that is built on or otherwise developed" is a dictionary definition that I found online. To me, it would imply either rural or an extremely unpopulated area -- but that would just be a guess.