Rails Model Namespaces: Could not find table - ruby-on-rails

Question

This is not a duplicate of 'How do I explicitly specify a Model's table-name mapping in Rails?', as I am looking for a way to not explicitly set the table names. Instead I want to automatically set the table names accordingly to the inheritance of a model.
I've got the following model structure:
models
First (inheritance)
Second (inheritance)
Third (model)
User (model)
Second (model)
I have the following tables in the database:
first_second_thirds
users
user_seconds
When I execute the following code:
First::Second::Third.create(id: 1)
User.create(id: 1)
User::Second.create(id: 1)
I get that error:
ActiveRecord::StatementInvalid: Could not find table 'thirds'
How do I tell the model the appropriate database table?
EDIT: Adding Code Examples
db/migrate/20170305200503_create_first_second_third.rb
class CreateFirstSecondThirds < ActiveRecord::Migration[5.0]
def change
create_table :first_second_thirds do |t|
t.timestamps
end
end
end
db/migrate/20161114164114_devise_create_users.rb
class DeviseCreateUsers < ActiveRecord::Migration[5.0]
def change
create_table :users do |t|
t.timestamps
end
end
end
db/migrate/20170305145804_create_user_stories.rb
class CreateUserSeconds < ActiveRecord::Migration[5.0]
def change
create_table :user_seconds do |t|
t.timestamps
end
end
end
app/models/first/second/third.rb
class User < ApplicationRecord
end
app/models/user.rb
class User < ApplicationRecord
end
app/models/user/second.rb
class User < ApplicationRecord
end