class Rubocop::Cop::Style::ClassAndModuleCamelCase

an underscore in them.
This cops checks for class and module names with

def check_name(node) 

def check_name(node)
  name = node.loc.name.source
  add_offense(node, :name) if name =~ /_/
end

def on_class(node) 

def on_class(node)
  check_name(node)
end

def on_module(node) 

def on_module(node)
  check_name(node)
end