Display product category names in Woocommerce order details

// Display order items product categories (Orders on front end and emails)
add_action( 'woocommerce_order_item_meta_end', 'display_custom_data_in_emails', 10, 4 );
function display_custom_data_in_emails( $item_id, $item, $order, $bool ) {
    // Get the product categories for this item
    $terms = wp_get_post_terms( $item->get_product_id(), 'product_cat', array( 'fields' => 'names' ) );

    // Output a coma separated string of product category names
    echo "<br><small>" . implode(', ', $terms) . "</small>";
}

// Display order items product categories in admin order edit pages
add_action( 'woocommerce_after_order_itemmeta', 'custom_admin_order_itemmeta', 15, 3 );
function custom_admin_order_itemmeta( $item_id, $item, $product ){
    //if( ! is_admin() ) return; // only backend

    // Target order "line items" only to avoid errors
    if( $item->is_type( 'line_item' ) ){
        // Get the product categories for this item
        $terms = wp_get_post_terms( $item->get_product_id(), 'product_cat', array( 'fields' => 'names' ) );

        // Output a coma separated string of product category names
        echo "<br><small>" . implode(', ', $terms) . "</small>";
    }
}