Uninitialized constant for grape

I am using grape in rails and i'm getting the following error.

Uninitialized constant TMO.

I have this folder structure in grape app/tmo/root.rb and inside the root.rb file i have this code and when i try to mount i get the following error occurs - Unintialized constant TMO.

module TMO
  class Root < ::Grape::API
  end
end

when i make it to tmo and mount in routes its working.Is it possible to use the GIS or i should use Gis and why