you question as not been fully answered. By the first two answers
The land immediately next to, and inland from, a coast. <-(1) only one meaning as described BUT see other meanings below.
The rural territory surrounding an urban area, especially a port.
A remote or undeveloped area, a backwater.<-- does not have to be near the coast
(figuratively) That which is unknown or unexplored about someone.
(figuratively) Anything vague or ill-defined, especially one that is ill understood.
* 2007 , Lesley Jeffries, Textual Construction of the Female Body , abstract
This approach utilizes concepts such as naming, describing, contrasting and equating to access the hinterland between structure and meaning, and to map out the subtle ways in which texts can naturalise the ideology of the perfect female form.
HINTER German = behind, back (land behind back of)