diff --git a/lib/yard/core_ext/module.rb b/lib/yard/core_ext/module.rb
index 6f0b95105..93fef9d9a 100644
--- a/lib/yard/core_ext/module.rb
+++ b/lib/yard/core_ext/module.rb
@@ -8,13 +8,4 @@ class Module
   def class_name
     name.split("::").last
   end
-
-  # Returns the module namespace path minus the class/module name
-  #
-  # @example
-  #   module A::B::C; namespace_name end # => "A::B"
-  # @return [String] the namespace minus the class/module name
-  def namespace_name
-    name.split("::")[0..-2].join("::")
-  end
 end
diff --git a/po/ja.po b/po/ja.po
index 9e45fd661..199fb1486 100644
--- a/po/ja.po
+++ b/po/ja.po
@@ -15043,16 +15043,6 @@ msgstr ""
 msgid "the last part of a module path"
 msgstr "モジュールパスの最後の部分"
 
-# Module#namespace_name
-#: ../lib/yard/core_ext/module.rb:12
-msgid "Returns the module namespace path minus the class/module name"
-msgstr "クラス/モジュール名を引いたモジュールのnamespaceのパスを返す"
-
-# @example 
-#: ../lib/yard/core_ext/module.rb:16
-msgid "module A::B::C; namespace_name end # => \"A::B\""
-msgstr ""
-
 # @return [String]
 #: ../lib/yard/core_ext/module.rb:16
 msgid "the namespace minus the class/module name"
diff --git a/spec/core_ext/module_spec.rb b/spec/core_ext/module_spec.rb
index f7de3c769..a9d49bcea 100644
--- a/spec/core_ext/module_spec.rb
+++ b/spec/core_ext/module_spec.rb
@@ -6,10 +6,4 @@
       expect(YARD::CodeObjects::Base.class_name).to eq "Base"
     end
   end
-
-  describe "#namespace" do
-    it "returns everything before the class name" do
-      expect(YARD::CodeObjects::Base.namespace_name).to eq "YARD::CodeObjects"
-    end
-  end
 end