What is the origin of the idiom "hit the hay" and when to use it?

The idiom "hit the hay" has its origin in the practice of using hay as a common and simple material for making mattresses or bedding in rural areas during the 19th century. The expression captures the idea of going to sleep, often after a day of work or exhaustion, and resting on a bed made of hay. Over time, the phrase has been widely adopted to signify the act of going to sleep or retiring for the night.