"免费赠送" 的英文表达是 "give away for free" 或 "offer for free"。这个短语的来源可能源自商家或机构给消费者或客户免费提供商品或服务的做法。

例句：

我们正在免费赠送一份旅游手册。(We are giving away a travel guide for free.)

这家商店正在免费赠送一些样品。(The store is offering some samples for free.)

我们在活动中免费赠送了一台电脑。(We gave away a computer for free as part of the promotion.)