: While the term existed earlier, it surged in popularity during World War II. Soldiers frequently used "sack" as slang for their sleeping bags.

The phrase has roots in both historical bedding practices and military slang:

: Some sources trace the slang use of "sack" for a bunk or bed back to naval contexts as early as 1825. Usage and Examples

"Hit the sack" is a popular informal idiom that means . It is often used when someone is feeling particularly exhausted after a long day. Origin and History

: In the late 19th and early 20th centuries, mattresses were often just large cloth sacks stuffed with hay or straw. "Hitting the sack" was a literal description of laying down on these improvised beds.