Source

File: wp-includes/widgets/class-wp-widget-archives.php

public function __construct() {
		$widget_ops = array(
			'classname'                   => 'widget_archive',
			'description'                 => __( 'A monthly archive of your site’s Posts.' ),
			'customize_selective_refresh' => true,
		);
		parent::__construct( 'archives', __( 'Archives' ), $widget_ops );
	}