diff --git a/core/lib/Drupal/Component/Render/MarkupInterface.php b/core/lib/Drupal/Component/Render/MarkupInterface.php
index 88f0ed7..2da4e13 100644
--- a/core/lib/Drupal/Component/Render/MarkupInterface.php
+++ b/core/lib/Drupal/Component/Render/MarkupInterface.php
@@ -16,8 +16,8 @@
  * If there is any risk of the object's __toString() method returning
  * user-entered data that has not been filtered first, it must not be used. If
  * the object that implements this does not perform automatic escaping or
- * filtering itself, then it must be marked as @internal. For example, Views has
- * the internal ViewsRenderPipelineMarkup object to provide a custom render
+ * filtering itself, then it must be marked as "@internal". For example, Views
+ * has the internal ViewsRenderPipelineMarkup object to provide a custom render
  * pipeline in order to render JSON and to fast render fields. By contrast,
  * FormattableMarkup and TranslatableMarkup always sanitize their output when
  * used correctly.
diff --git a/core/lib/Drupal/Core/Field/AllowedTagsXssTrait.php b/core/lib/Drupal/Core/Field/AllowedTagsXssTrait.php
index 831d0df..c889615 100644
--- a/core/lib/Drupal/Core/Field/AllowedTagsXssTrait.php
+++ b/core/lib/Drupal/Core/Field/AllowedTagsXssTrait.php
@@ -12,7 +12,7 @@
  * @deprecated in Drupal 8.0.x, will be removed before Drupal 9.0.0. Use
  *   \Drupal\Core\Field\FieldFilteredMarkup instead.
  *
- * @see \Drupal\Core\Field\FieldFilteredString
+ * @see \Drupal\Core\Field\FieldFilteredMarkup
  */
 trait AllowedTagsXssTrait {
 
diff --git a/core/lib/Drupal/Core/Field/FieldFilteredMarkup.php b/core/lib/Drupal/Core/Field/FieldFilteredMarkup.php
index 18c3e71..78900a9 100644
--- a/core/lib/Drupal/Core/Field/FieldFilteredMarkup.php
+++ b/core/lib/Drupal/Core/Field/FieldFilteredMarkup.php
@@ -34,7 +34,7 @@
    * @return string|\Drupal\Component\Render\MarkupInterface
    *   A safe string filtered with the allowed tag list and normalized.
    *
-   * @see \Drupal\Core\Field\FieldFilteredString::allowedTags()
+   * @see \Drupal\Core\Field\FieldFilteredMarkup::allowedTags()
    * @see \Drupal\Component\Utility\Xss::filter()
    * @see \Drupal\Component\Utility\Html::normalize()
    */
diff --git a/core/modules/filter/src/Element/ProcessedText.php b/core/modules/filter/src/Element/ProcessedText.php
index de9d5cc..6a3fa40 100644
--- a/core/modules/filter/src/Element/ProcessedText.php
+++ b/core/modules/filter/src/Element/ProcessedText.php
@@ -14,7 +14,7 @@
 use Drupal\Core\Render\Renderer;
 use Drupal\filter\Entity\FilterFormat;
 use Drupal\filter\Plugin\FilterInterface;
-use Drupal\filter\Render\FilteredString;
+use Drupal\filter\Render\FilteredMarkup;
 
 /**
  * Provides a processed text render element.
@@ -127,7 +127,7 @@ public static function preRenderText($element) {
     // safe, but it has been passed through the filter system and checked with
     // a text format, so it must be printed as is. (See the note about security
     // in the method documentation above.)
-    $element['#markup'] = FilteredString::create($text);
+    $element['#markup'] = FilteredMarkup::create($text);
 
     // Set the updated bubbleable rendering metadata and the text format's
     // cache tag.
diff --git a/core/modules/filter/src/Plugin/Filter/FilterCaption.php b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
index 7671452..37c18cc 100644
--- a/core/modules/filter/src/Plugin/Filter/FilterCaption.php
+++ b/core/modules/filter/src/Plugin/Filter/FilterCaption.php
@@ -12,7 +12,7 @@
 use Drupal\Component\Utility\Xss;
 use Drupal\filter\FilterProcessResult;
 use Drupal\filter\Plugin\FilterBase;
-use Drupal\filter\Render\FilteredString;
+use Drupal\filter\Render\FilteredMarkup;
 
 /**
  * Provides a filter to caption elements.
@@ -45,7 +45,7 @@ public function process($text, $langcode) {
         // Sanitize caption: decode HTML encoding, limit allowed HTML tags; only
         // allow inline tags that are allowed by default, plus <br>.
         $caption = Html::decodeEntities($caption);
-        $caption = FilteredString::create(Xss::filter($caption, array('a', 'em', 'strong', 'cite', 'code', 'br')));
+        $caption = FilteredMarkup::create(Xss::filter($caption, array('a', 'em', 'strong', 'cite', 'code', 'br')));
 
         // The caption must be non-empty.
         if (Unicode::strlen($caption) === 0) {
@@ -62,7 +62,7 @@ public function process($text, $langcode) {
           // We pass the unsanitized string because this is a text format
           // filter, and after filtering, we always assume the output is safe.
           // @see \Drupal\filter\Element\ProcessedText::preRenderText()
-          '#node' => FilteredString::create($node->C14N()),
+          '#node' => FilteredMarkup::create($node->C14N()),
           '#tag' => $node->tagName,
           '#caption' => $caption,
           '#classes' => $classes,
diff --git a/core/modules/filter/src/Render/FilteredString.php b/core/modules/filter/src/Render/FilteredMarkup.php
similarity index 86%
rename from core/modules/filter/src/Render/FilteredString.php
rename to core/modules/filter/src/Render/FilteredMarkup.php
index 62b709d..2abfac3 100644
--- a/core/modules/filter/src/Render/FilteredString.php
+++ b/core/modules/filter/src/Render/FilteredMarkup.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\filter\Render\FilteredString.
+ * Contains \Drupal\filter\Render\FilteredMarkup.
  */
 
 namespace Drupal\filter\Render;
@@ -24,6 +24,6 @@
  *
  * @see \Drupal\Core\Render\Markup
  */
-final class FilteredString implements MarkupInterface, \Countable {
+final class FilteredMarkup implements MarkupInterface, \Countable {
   use MarkupTrait;
 }
diff --git a/core/tests/Drupal/Tests/Core/Field/FieldFilteredStringTest.php b/core/tests/Drupal/Tests/Core/Field/FieldFilteredMarkupTest.php
similarity index 93%
rename from core/tests/Drupal/Tests/Core/Field/FieldFilteredStringTest.php
rename to core/tests/Drupal/Tests/Core/Field/FieldFilteredMarkupTest.php
index ad74be7..c3a6e87 100644
--- a/core/tests/Drupal/Tests/Core/Field/FieldFilteredStringTest.php
+++ b/core/tests/Drupal/Tests/Core/Field/FieldFilteredMarkupTest.php
@@ -2,7 +2,7 @@
 
 /**
  * @file
- * Contains \Drupal\Tests\Core\Field\FieldFilteredStringTest.
+ * Contains \Drupal\Tests\Core\Field\FieldFilteredMarkupTest.
  */
 
 namespace Drupal\Tests\Core\Field;
@@ -15,7 +15,7 @@
  * @coversDefaultClass \Drupal\Core\Field\FieldFilteredMarkup
  * @group Field
  */
-class FieldFilteredStringTest extends UnitTestCase {
+class FieldFilteredMarkupTest extends UnitTestCase {
 
   /**
    * @covers ::create