In Tamil, and sometimes other southern languages, names end in '-an' when a person is named after a god, such as Ramnath, Badrinath, Narayan etc. These become Ramanathan, Badrinathan, Narayanan etc. the '-an' denotes that the person named is a mere mortal and not a God. An individual is not to be called Ramnath, Badrinath etc. because those are the names of the Gods, exclusively. 2. The Gods themselves are referred to Ramanath-ar, Badrinath-ar etc. the '-ar' being similar to '-ji' in Hindi, as in Badrinath-ji etc. 3. And when people pray in South India and address God directly, it becomes Narayan-a, Ramanath-a etc. the '-a' being a direct form of address, as in Sanskrit. 4. Under influence of North Indian culture, some of these conventions are easing, as you do sometimes see younger people with North Indian style religious names.
For example, Narayanan is shortened to Narayan, Ramanathan to Ramanath, etc. They are usually not aware that doing so usually offends the person affected, as the South Indian usually feels that the North Indian in question is being regionalistic and dismissive of other Indian's names, preferring the equivalents in their own (Hindi or Punjabi) language