It is interesting to see, how people would have recognized themselves in ancient times. India had lot of different kingdoms and different tribes and people migrating from one place to another. If a new tribe or people or person came to a new place/people/city, the new person/tribe/people will be asked "where do u come from?", a person coming from a lake(in ancient times lakes, rivers, etc. were major places for people travelling with animals) would say 'i come from a lake', so the person/tribe/ people will be recognized by 'Lake identity'. As the kingdoms and civilizations in ancient times were spread widely at vast distances, such migration place/object of nature, recognition would have been major identity of the tribes and people.
While "Meer" or "Mir" both the words are spelled same although written differently, in Indoeuropean sense this word means a lake/ sea. This word "Mir" or "Meer" is an indoeuropean word which shows direct connection to ancient migrations.