Rename Tabs in My Account 

add_filter ( 'woocommerce_account_menu_items', 'misha_rename_downloads' );

function misha_rename_downloads( $menu_links ){
	
	// $menu_links['TAB ID HERE'] = 'NEW TAB NAME HERE';
	$menu_links['downloads'] = 'My Files';

	return $menu_links;
}