Translate MCE button text/tooltip in custom plugin

Create js file button.js and add js directory and list-btn.png needed

(function() {
    tinymce.create("tinymce.plugins.listbuttons_button_plugin", {

        //url argument holds the absolute url of our plugin directory
        init : function(ed, url) {

            //add new button    
            ed.addButton("listbuttons", {
                title : "Add Related post shortcode",
                cmd : "listbuttons_command",
                image : "images/list-btn.png"
            });

            ed.addCommand("listbuttons_command", function() {
                var return_text = "[related]";
                ed.execCommand("mceInsertContent", 0, return_text);
            });

        },

        createControl : function(n, cm) {
            return null;
        },
        getInfo : function() {}
    });

    tinymce.PluginManager.add("listbuttons_button_plugin", tinymce.plugins.listbuttons_button_plugin);
})();

Add Code in Function.php

function enqueue_plugin_scripts($plugin_array){
    $plugin_array["listbuttons_button_plugin"] =  get_template_directory_uri() . "/js/buttons.js";
    return $plugin_array;
}
add_filter("mce_external_plugins", "enqueue_plugin_scripts");

function register_buttons_editor($buttons){
    array_push($buttons, "listbuttons");
    return $buttons;
}
add_filter("mce_buttons", "register_buttons_editor");

function shortcode_button_script(){
    if(wp_script_is("quicktags")){
        ?>
            <script type="text/javascript">
                QTags.addButton("list_buttons_shortcode","Add Related post shortcode",callback);
                function callback(){
                    QTags.insertContent("[listbuttons]");
                }
            </script>
        <?php
    }
}
add_action("admin_print_footer_scripts", "shortcode_button_script");