gistfile1.txt

add_filter( 'gettext', 'propertyhive_book_viewing_label', 99, 3 );
function propertyhive_book_viewing_label( $translated_text, $text, $domain ) {

    switch ( $translated_text ) 
    {
        case 'Book Viewing' :
        {
            $translated_text = 'My Viewing Button label Here';
            break;
        }
    }

    return $translated_text;
}