I don't believe you can change that. The recommended method would be to delete it and create a new one.
i was going to create the new fields with proper naming but just wondering what will happen to the existing data that is already saved in the database under the field names group1, group2
When i will create new attribute, it will create a new field in the database which is fine, but the issue is with existing saved data
The data that is in those existing fields will stay in those existing fields. You could execute a script that will copy from one field to another.
Set usr_newgroup = usr_group1
Hope this clarifies.