Changing "hoover" text when I hold the mouse on the four featured content images

Running latest WP and theme ver at fleksjobbernetvaerket.dk When I hold the mouse over the four featured content images, that slides on my front page - each and everyone says : featured-image-x* where x is a 1-4 .... I have four pictures there to show. Where do I change that to ... a text of my own choosing