prefix_name_for_action

# File actionpack/lib/action_dispatch/routing/mapper.rb, line 1830
          def prefix_name_for_action(as, action)
            if as
              prefix = as
            elsif !canonical_action?(action)
              prefix = action
            end

            if prefix && prefix != "/" && !prefix.empty?
              Mapper.normalize_name prefix.to_s.tr("-", "_")
            end
          end