"Forget" 是 "忘记" 的意思，"to do" 是"去做某事"的意思，所以 "忘记去做某事" 用英语可以说成 "forget to do something"。
下面是一些例句：
I forgot to take out the trash. (我忘记倒垃圾了。)
She forgot to lock the door. (她忘记锁门了。)
He forgot to call his mother. (他忘记给他妈妈打电话了。)
它的来源是英语中"forget" 和 "to do" 两个词组合在一起使用。