diff --git a/dom/base/ChromeUtils.cpp b/dom/base/ChromeUtils.cpp
index 9632c355b193..b7d22364e3ef 100644
--- a/dom/base/ChromeUtils.cpp
+++ b/dom/base/ChromeUtils.cpp
@@ -16,7 +16,6 @@
 
 #include "mozilla/Base64.h"
 #include "mozilla/CycleCollectedJSRuntime.h"
-#include "mozilla/ErrorNames.h"
 #include "mozilla/EventStateManager.h"
 #include "mozilla/IntentionalCrash.h"
 #include "mozilla/PerformanceMetricsCollector.h"
@@ -291,12 +290,6 @@ void ChromeUtils::AddProfilerMarker(
   }
 }
 
-/* static */
-void ChromeUtils::GetXPCOMErrorName(GlobalObject& aGlobal, uint32_t aErrorCode,
-                                    nsACString& aRetval) {
-  GetErrorName((nsresult)aErrorCode, aRetval);
-}
-
 /* static */
 void ChromeUtils::WaiveXrays(GlobalObject& aGlobal, JS::HandleValue aVal,
                              JS::MutableHandleValue aRetval, ErrorResult& aRv) {
diff --git a/dom/base/ChromeUtils.h b/dom/base/ChromeUtils.h
index 47435e516a00..4de8d799a9cb 100644
--- a/dom/base/ChromeUtils.h
+++ b/dom/base/ChromeUtils.h
@@ -88,9 +88,6 @@ class ChromeUtils {
                                 const ProfilerMarkerOptionsOrDouble& aOptions,
                                 const Optional<nsACString>& text);
 
-  static void GetXPCOMErrorName(GlobalObject& aGlobal, uint32_t aErrorCode,
-                                nsACString& aRetval);
-
   static void OriginAttributesToSuffix(
       GlobalObject& aGlobal, const dom::OriginAttributesDictionary& aAttrs,
       nsCString& aSuffix);
diff --git a/dom/base/test/unit/test_chromeutils_getXPCOMErrorName.js b/dom/base/test/unit/test_chromeutils_getXPCOMErrorName.js
deleted file mode 100644
index f7d6a89e7187..000000000000
--- a/dom/base/test/unit/test_chromeutils_getXPCOMErrorName.js
+++ /dev/null
@@ -1,40 +0,0 @@
-"use strict";
-
-// Test ChromeUtils.getXPCOMErrorName
-
-add_task(function test_getXPCOMErrorName() {
-  info("Force the initialization of NSS to get the error names right");
-  Cc["@mozilla.org/psm;1"].getService(Ci.nsISupports);
-
-  Assert.equal(
-    ChromeUtils.getXPCOMErrorName(Cr.NS_OK),
-    "NS_OK",
-    "getXPCOMErrorName works for NS_OK"
-  );
-
-  Assert.equal(
-    ChromeUtils.getXPCOMErrorName(Cr.NS_ERROR_FAILURE),
-    "NS_ERROR_FAILURE",
-    "getXPCOMErrorName works for NS_ERROR_FAILURE"
-  );
-
-  const nssErrors = Cc["@mozilla.org/nss_errors_service;1"].getService(
-    Ci.nsINSSErrorsService
-  );
-  Assert.equal(
-    ChromeUtils.getXPCOMErrorName(
-      nssErrors.getXPCOMFromNSSError(Ci.nsINSSErrorsService.NSS_SEC_ERROR_BASE)
-    ),
-    "NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, SEC_ERROR_IO)",
-    "getXPCOMErrorName works for NSS_SEC_ERROR_BASE"
-  );
-  // See https://searchfox.org/mozilla-central/rev/a48e21143960b383004afa9ff9411c5cf6d5a958/security/nss/lib/util/secerr.h#20
-  const SEC_ERROR_BAD_DATA = Ci.nsINSSErrorsService.NSS_SEC_ERROR_BASE + 2;
-  Assert.equal(
-    ChromeUtils.getXPCOMErrorName(
-      nssErrors.getXPCOMFromNSSError(SEC_ERROR_BAD_DATA)
-    ),
-    "NS_ERROR_GENERATE_FAILURE(NS_ERROR_MODULE_SECURITY, SEC_ERROR_BAD_DATA)",
-    "getXPCOMErrorName works for NSS's SEC_ERROR_BAD_DATA"
-  );
-});
diff --git a/dom/base/test/unit/xpcshell.ini b/dom/base/test/unit/xpcshell.ini
index 2301fb041a9a..d54bc903ae8b 100644
--- a/dom/base/test/unit/xpcshell.ini
+++ b/dom/base/test/unit/xpcshell.ini
@@ -54,7 +54,6 @@ head = head_xml.js
 [test_xmlserializer.js]
 [test_cancelPrefetch.js]
 [test_chromeutils_base64.js]
-[test_chromeutils_getXPCOMErrorName.js]
 [test_chromeutils_shallowclone.js]
 [test_generate_xpath.js]
 head = head_xml.js
diff --git a/dom/chrome-webidl/ChromeUtils.webidl b/dom/chrome-webidl/ChromeUtils.webidl
index 7dd0af307f74..dfa3b343f1b2 100644
--- a/dom/chrome-webidl/ChromeUtils.webidl
+++ b/dom/chrome-webidl/ChromeUtils.webidl
@@ -233,12 +233,6 @@ namespace ChromeUtils {
                          optional (ProfilerMarkerOptions or DOMHighResTimeStamp) options = {},
                          optional UTF8String text);
 
-  /**
-   * Return the symbolic name of any given XPCOM error code (nsresult):
-   * "NS_OK", "NS_ERROR_FAILURE",...
-   */
-  UTF8String getXPCOMErrorName(unsigned long aErrorCode);
-
   /**
    * IF YOU ADD NEW METHODS HERE, MAKE SURE THEY ARE THREAD-SAFE.
    */
diff --git a/xpcom/base/ErrorNames.cpp b/xpcom/base/ErrorNames.cpp
index 663fd6823ff0..c1540d4bd333 100644
--- a/xpcom/base/ErrorNames.cpp
+++ b/xpcom/base/ErrorNames.cpp
@@ -47,7 +47,7 @@ void GetErrorName(nsresult rv, nsACString& name) {
   name.AppendLiteral(", ");
 
   const char* nsprName = nullptr;
-  if (isSecurityError && NS_IsMainThread()) {
+  if (isSecurityError) {
     // Invert the logic from NSSErrorsService::GetXPCOMFromNSSError
     PRErrorCode nsprCode = -1 * static_cast<PRErrorCode>(NS_ERROR_GET_CODE(rv));
     nsprName = PR_ErrorToName(nsprCode);