How to rename “Publish” metabox title in post screen

The best way would be to remove the meta box and then add it back in with your new title:

function change_publish_meta_box() {
    remove_meta_box( 'submitdiv', 'post', 'side' );
    add_meta_box( 'submitdiv', 'YOUR TITLE HERE', 'post_submit_meta_box', null, 'side', 'high' );
}
add_action( 'add_meta_boxes_post',  'change_publish_meta_box' );

(Change YOUR TITLE HERE to whatever you want)