diff --git a/core/lib/Drupal/Core/Form/FormBuilder.php b/core/lib/Drupal/Core/Form/FormBuilder.php
index 382bba1..5e36b19 100644
--- a/core/lib/Drupal/Core/Form/FormBuilder.php
+++ b/core/lib/Drupal/Core/Form/FormBuilder.php
@@ -244,9 +244,9 @@ public function buildForm($form_id, FormStateInterface &$form_state) {
       }
     }
 
-    // If this form should post to the original URL, disable all form redirects.
+    // If this form is an AJAX request, disable all form redirects.
     $request = $this->requestStack->getCurrentRequest();
-    if ($post_to_original_url = $request->query->has(static::POST_TO_ORIGINAL_URL)) {
+    if ($ajax_form_request = $request->query->has(static::AJAX_FORM_REQUEST)) {
       $form_state->disableRedirect();
     }
 
@@ -263,14 +263,14 @@ public function buildForm($form_id, FormStateInterface &$form_state) {
     // can use it to know or update information about the state of the form.
     $response = $this->processForm($form_id, $form, $form_state);
 
-    // After processing the form, if this is to be posted to the original URL,
-    // interrupt form rendering and return by throwing an exception that
-    // contains the processed form and form state. This exception will be caught
-    // by \Drupal\Core\Form\EventSubscriber\FormAjaxSubscriber::onException()
-    // and then passed through
+    // After processing the form, if this is an AJAX form request, interrupt
+    // form rendering and return by throwing an exception that contains the
+    // processed form and form state. This exception will be caught by
+    // \Drupal\Core\Form\EventSubscriber\FormAjaxSubscriber::onException() and
+    // then passed through
     // \Drupal\Core\Form\FormAjaxResponseBuilderInterface::buildResponse() to
     // build a proper AJAX response.
-    if ($post_to_original_url) {
+    if ($ajax_form_request) {
       throw new FormAjaxException($form, $form_state);
     }
 
diff --git a/core/lib/Drupal/Core/Form/FormBuilderInterface.php b/core/lib/Drupal/Core/Form/FormBuilderInterface.php
index 76d3342..9178278 100644
--- a/core/lib/Drupal/Core/Form/FormBuilderInterface.php
+++ b/core/lib/Drupal/Core/Form/FormBuilderInterface.php
@@ -13,9 +13,9 @@
 interface FormBuilderInterface {
 
   /**
-   * Request key for a form that will post to original URL on AJAX submission.
+   * Request key for a form that was triggered via AJAX.
    */
-  const POST_TO_ORIGINAL_URL = 'post_to_original_url';
+  const AJAX_FORM_REQUEST = 'ajax_form';
 
   /**
    * Determines the ID of a form.
diff --git a/core/lib/Drupal/Core/Render/Element/RenderElement.php b/core/lib/Drupal/Core/Render/Element/RenderElement.php
index 623f418..039a19f 100644
--- a/core/lib/Drupal/Core/Render/Element/RenderElement.php
+++ b/core/lib/Drupal/Core/Render/Element/RenderElement.php
@@ -241,7 +241,7 @@ public static function preRenderAjaxForm($element) {
       // re-rendering. For that, we have a special 'system/ajax' route.
       if (isset($settings['callback']) && !isset($settings['url'])) {
         $settings['url'] = Url::fromRoute('<current>');
-        $settings['options']['query'][FormBuilderInterface::POST_TO_ORIGINAL_URL] = TRUE;
+        $settings['options']['query'][FormBuilderInterface::AJAX_FORM_REQUEST] = TRUE;
       }
       $settings += array(
         'url' => NULL,
diff --git a/core/modules/system/src/Tests/Ajax/DialogTest.php b/core/modules/system/src/Tests/Ajax/DialogTest.php
index 603cfa0..fbe586c 100644
--- a/core/modules/system/src/Tests/Ajax/DialogTest.php
+++ b/core/modules/system/src/Tests/Ajax/DialogTest.php
@@ -166,7 +166,7 @@ public function testDialog() {
       'edit-preview' => [
         'callback' => '::preview',
         'event' => 'click',
-        'url' => Url::fromRoute('ajax_test.dialog_form')->setOption('query', [FormBuilderInterface::POST_TO_ORIGINAL_URL => TRUE])->toString(),
+        'url' => Url::fromRoute('ajax_test.dialog_form')->setOption('query', [FormBuilderInterface::AJAX_FORM_REQUEST => TRUE])->toString(),
         'dialogType' => 'ajax',
         'submit' => [
           '_triggering_element_name' => 'op',