// tausche
$data = '<a href="'.$tmp->url.'">'.$image.$tmp->name.'</a>';

//gegen
$data = '<a href="'.$tmp->url.'" title="'.$item->name.'">'.$image.$tmp->name.'</a>';

http://www.gn-webdesign.de/joomla-tutorials/mainmenu-title-attribut.html

/modules/mod_mainmenu/helper.php
line 349

joomla menu title tag

joomla

PHP