diff -u b/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
--- b/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -614,6 +614,9 @@
  *   unit tests with a clean environment.
  */
 function drupal_static_reset($name = NULL) {
+  if ($name === 'taxonomy_vocabulary_get_names') {
+    @trigger_error("Using drupal_static_reset() with 'taxonomy_vocabulary_get_names' as parameter is deprecated in Drupal 9.1.0 and will be removed before Drupal 10.0.0. There's no replacement for this usage. See https://www.drupal.org/node/3039041.", E_USER_DEPRECATED);
+  }
   drupal_static($name, NULL, TRUE);
 }
 
@@ -979,9 +982,6 @@
  *   unit tests with a clean environment.
  */
 function drupal_static_reset($name = NULL) {
-  if ($name === 'taxonomy_vocabulary_get_names') {
-    @trigger_error("Using drupal_static_reset() with 'taxonomy_vocabulary_get_names' as parameter is deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. There's no replacement for this usage. See https://www.drupal.org/node/3039041.", E_USER_DEPRECATED);
-  }
   drupal_static($name, NULL, TRUE);
 }
 
diff -u b/core/modules/taxonomy/taxonomy.module b/core/modules/taxonomy/taxonomy.module
--- b/core/modules/taxonomy/taxonomy.module
+++ b/core/modules/taxonomy/taxonomy.module
@@ -211,20 +211,17 @@
  *
  * @return array
  *   A list of existing vocabulary IDs.
+ *
+ * @deprecated in Drupal 9.1.0 and will be removed before Drupal 10.0.0. Use
+ *   \Drupal::entityTypeManager()->getStorage('taxonomy_vocabulary')->loadMultiple()
+ *   instead, to get a list of vocabulary entities keyed by vocabulary ID.
+ *
+ * @see https://www.drupal.org/node/3039041
  */
 function taxonomy_vocabulary_get_names() {
-  $names = &drupal_static(__FUNCTION__);
-
-  if (!isset($names)) {
-    $names = [];
-    $config_names = \Drupal::configFactory()->listAll('taxonomy.vocabulary.');
-    foreach ($config_names as $config_name) {
-      $id = substr($config_name, strlen('taxonomy.vocabulary.'));
-      $names[$id] = $id;
-    }
-  }
-
-  return $names;
+  @trigger_error('taxonomy_vocabulary_get_names() is deprecated in Drupal 9.1.0 and will be removed before Drupal 10.0.0. Use \Drupal::entityTypeManager()->getStorage("taxonomy_vocabulary")->loadMultiple() instead, to get a list of vocabulary entities keyed by vocabulary ID. See https://www.drupal.org/node/3039041.', E_USER_DEPRECATED);
+  $vids = array_keys(\Drupal::entityTypeManager()->getStorage('taxonomy_vocabulary')->loadMultiple());
+  return array_combine($vids, $vids);
 }
 
 /**
@@ -244,14 +241,7 @@
 function taxonomy_term_load_multiple_by_name($name, $vocabulary = NULL) {
   $values = ['name' => trim($name)];
   if (isset($vocabulary)) {
-    $vocabularies = taxonomy_vocabulary_get_names();
-    if (isset($vocabularies[$vocabulary])) {
-      $values['vid'] = $vocabulary;
-    }
-    else {
-      // Return an empty array when filtering by a non-existing vocabulary.
-      return [];
-    }
+    $values['vid'] = $vocabulary;
   }
   return \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties($values);
 }
@@ -307,17 +297,20 @@
  *
  * @return array
  *   A list of existing vocabulary IDs.
- *
- * @deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. Use
- *   \Drupal::entityTypeManager()->getStorage('taxonomy_vocabulary')->loadMultiple()
- *   instead, to get a list of vocabulary entities keyed by vocabulary ID.
- *
- * @see https://www.drupal.org/node/3039041
  */
 function taxonomy_vocabulary_get_names() {
-  @trigger_error('taxonomy_vocabulary_get_names() is deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. Use \Drupal::entityTypeManager()->getStorage("taxonomy_vocabulary")->loadMultiple() instead, to get a list of vocabulary entities keyed by vocabulary ID. See https://www.drupal.org/node/3039041.', E_USER_DEPRECATED);
-  $vids = array_keys(\Drupal::entityTypeManager()->getStorage('taxonomy_vocabulary')->loadMultiple());
-  return array_combine($vids, $vids);
+  $names = &drupal_static(__FUNCTION__);
+
+  if (!isset($names)) {
+    $names = [];
+    $config_names = \Drupal::configFactory()->listAll('taxonomy.vocabulary.');
+    foreach ($config_names as $config_name) {
+      $id = substr($config_name, strlen('taxonomy.vocabulary.'));
+      $names[$id] = $id;
+    }
+  }
+
+  return $names;
 }
 
 /**
@@ -337,7 +330,14 @@
 function taxonomy_term_load_multiple_by_name($name, $vocabulary = NULL) {
   $values = ['name' => trim($name)];
   if (isset($vocabulary)) {
-    $values['vid'] = $vocabulary;
+    $vocabularies = taxonomy_vocabulary_get_names();
+    if (isset($vocabularies[$vocabulary])) {
+      $values['vid'] = $vocabulary;
+    }
+    else {
+      // Return an empty array when filtering by a non-existing vocabulary.
+      return [];
+    }
   }
   return \Drupal::entityTypeManager()->getStorage('taxonomy_term')->loadByProperties($values);
 }
diff -u b/core/modules/taxonomy/tests/src/Unit/TaxonomyVocabularyTest.php b/core/modules/taxonomy/tests/src/Unit/TaxonomyVocabularyTest.php
--- b/core/modules/taxonomy/tests/src/Unit/TaxonomyVocabularyTest.php
+++ b/core/modules/taxonomy/tests/src/Unit/TaxonomyVocabularyTest.php
@@ -14,7 +14,7 @@
 
   /**
    * @group legacy
-   * @expectedDeprecation taxonomy_vocabulary_get_names() is deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. Use \Drupal::entityTypeManager()->getStorage("taxonomy_vocabulary")->loadMultiple() instead, to get a list of vocabulary entities keyed by vocabulary ID. See https://www.drupal.org/node/3039041.
+   * @expectedDeprecation taxonomy_vocabulary_get_names() is deprecated in Drupal 9.1.0 and will be removed before Drupal 10.0.0. Use \Drupal::entityTypeManager()->getStorage("taxonomy_vocabulary")->loadMultiple() instead, to get a list of vocabulary entities keyed by vocabulary ID. See https://www.drupal.org/node/3039041.
    * @see taxonomy_vocabulary_get_names()
    */
   public function testTaxonomyVocabularyGetNamesDeprecation() {
@@ -33,7 +33,7 @@
 
   /**
    * @group legacy
-   * @expectedDeprecation Using drupal_static_reset() with 'taxonomy_vocabulary_get_names' as parameter is deprecated in Drupal 8.8.0 and will be removed before Drupal 9.0.0. There's no replacement for this usage. See https://www.drupal.org/node/3039041.
+   * @expectedDeprecation Using drupal_static_reset() with 'taxonomy_vocabulary_get_names' as parameter is deprecated in Drupal 9.1.0 and will be removed before Drupal 10.0.0. There's no replacement for this usage. See https://www.drupal.org/node/3039041.
    * @see drupal_static_reset()
    */
   public function testTaxonomyVocabularyGetNamesCacheResetDeprecation() {