According to Rajiv Satyanarayana, a Student of Indian History, the name NorthEast India is related to cultural or historical; and not geographical. He wrote – ” I am amused at some people trying to find the geographical center of India and then arguing what different regions should be called”.

The name originated because they were the North-east frontier of Bengal, from where the British were based till 1911. You can see it in this 19th century book by explorer Sir Alexander Mckenzie. The North-east Frontier of India

He goes on to include all 7 modern states as North-east frontier.

Later we needed a term to denote the region of Assam and its sister states. The word Eastern India was already appropriated by the population centers of Orissa, Bengal and Bihar. So the term Northeast stuck for Assam and its sister states. East Bengal separating into another country made a distinct name all the more necessary for the seven states.

Rajiv Satyanarayana said – “Such things happen all the time, all over the world. I live in San Francisco which is called Northern California. That is fine except, it is not exactly Northern California: there is 400 miles of California more to the North. But the land further is empty: so we are good for now. If at all people begin to live there is big numbers, we will have to invent a word for that region and it cannot be Northern California because that word is already taken”.

Rajiv Satyanarayana gave more example and wrote , “To give one more example that geographical naming can be cultural too, these days we use the term South India based on whether that area speaks Dravidian languages predominantly or not.

Kolhapur 16.71° N, Sindhudurg 16.34° N, Panaji 15.49° N – NOT South India.

Gulbarga 17.33° N, Visakhapatnam 17.69° N, Karimnagar 18.44° N – YES South India”.

One final instance where naming is geographically haywire: Indian Railways. Southern Railways is based out of Chennai, South Western Railways out of Hubballi, South Central out of Secunderabad, but South Eastern out of Calcutta.