Question

Why we tell South-east and not East-south.....

Answer 1

we tell south - west, north- west because , the points or places are in between of Direction's .It means the directions are in the middle of 2 directions.

Answer 2

There is a fair amount of arbitrariness in the world, so there may not be an ultimate answer; but it is presumably most dependent on the fact that north, for us, is the principal direction, and other directions are seen as relative to that.  The preference for north is partially arbitrary as well; other orientations are possible, and the word ‘orientation’ originally referred to the east (as in ‘the Orient’), which was the principal direction when the word came into use.  The primacy of north for us is probably derivative of the North Star, or Polaris, whose position in the night sky is fairly constant and was an important navigational tool.  Since north is our principal direction, ‘northeast’ and ‘northwest’ were to be expected, and then ‘southeast’ and ‘southwest’ would logically follow by analogy.
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