to rock a baby (= to move it backwards and forwards or from side to side in a regular way) to help it to sleep

The Czech word for a lullaby is derived from the verb kolébat, meaning to rock-a-bye. 捷克语中“摇篮曲”这个词来源于动词kolébat，意思是“摇啊摇，哄婴儿睡觉”。

a well-known lullaby called "Rockabye Baby" 一首叫《摇啊摇，小宝宝》的著名摇篮曲

used to describe the action of rocking a baby to sleep, or something that relates to this

He was holding a big plank of wood in his arms rock-a-bye style. 他怀里抱着一大块木板，像在哄婴儿睡觉一样。