Theme_My_Login_Widget::__construct()

public function __construct() {
    parent::__construct(
        'theme-my-login',
        __( 'Theme My Login', 'theme-my-login' ),
        array(
            'classname'   => 'widget_theme_my_login',
            'description' => __( 'A login form for your site.', 'theme-my-login' ),
        )
    );
}

View src/includes/class-theme-my-login-widget.php, line 22 on GitHub