PrestaShop 1.6.x How to display full language name instead of its ISO code (and vice versa) in the language switcher

1. Access your server via any FTP client software or File Manager in your cPanel.
2. Go to /themes/themeXXXX/modules/blocklanguages/  directory, where XXXX is the number of your theme: 
3. Open blocklanguages.tpl file for editing. Find the following code:

Replace {$language.iso_code} with {$language.name|regex_replace:”/\s.*$/”:””};

You have changed ISO code to full language name in the language folder.

To change full language name to ISO code back, simply revert the changes done to blocklanguages.tpl file.

Hopefully, this tutorial was helpful for you.