Change Text inside Mobile Menu

When activated the mobile menu typically displays the “select-icons.png” image on the right & also the current page’s title on the left. I am wondering if it is possible to remove the current page title on the left hand side. I would like to replace it with the word menu.

I expect this can’t be done with CSS and I will have to edit one of my child theme’s php files. But I can’t find the code to change. How can I change the default text in the mobile menu?