Steps to reproduce the issue

1. The plugin is searching for a commonwords file like in that folder(/administrator)/language/xx-xx/xx-xx.com_finder.commonwords.txt
   

   joomla-cms/plugins/extension/finder/finder.php

   Lines 139 to 143 in 9cbe6cb

   	if ($extension->client_id == 0) {
   	$path = JPATH_SITE . '/language/' . $extension->element . '/' . $extension->element . '.com_finder.commonwords.txt';
   	} else {
   	$path = JPATH_ADMINISTRATOR . '/language/' . $extension->element . '/' . $extension->element . '.com_finder.commonwords.txt';
   	}

   
   The core file (for lang en-GB) was renamed from language/en-GB/en-GB.com_finder.commonwords.txt to language/en-GB/com_finder.commonwords.txt in PR #27130

2. A language pack consists of three parts site, admin, api. Even if the site language contains the file (with correct file name), they will be deleted again if the admin/api language is installed afterwards
   

   joomla-cms/plugins/extension/finder/finder.php

   Lines 57 to 60 in 9cbe6cb

   	if ($extension) {
   	$this->removeCommonWords($extension);
   	$this->addCommonWords($extension);
   	}

Expected result

Plugin should work as expected (when commonwords are needed)

Actual result

• clean installation
• check database #___finder_terms_common
• some values for "en" are present
• install an en lang pack for example (en-US)
• check database #___finder_terms_common
• values are deleted
• install any other lang pack
• table is still empty

System information (as much as possible)

J4.x

cc @Hackwar