por Thomas » 23 Jun 2010, 17:38
Gabi, you ask a good question. Here is my guess.
A "bunk" is a small bed, the type found in military barracks, on ships, etc. (Let me explain that a bunk can be just one bed. If there are two bunks, one is probably on top of the other like "beliches". Often, but not always. "Bunkbeds" mean that: one above the other. "Bunk", however, could mean one bed or a set of two.) I think the word is more used by men because bunks are more common in a man's world. In cowboy movies, for example, you will hear them talk about "the bunkhouse". That merely means "dormitory", the place where the cowboys slept while at the main part of the ranch.
In the old days, a "sack" filled with straw was often used as a mattress. Note how similar this concept is to "to hit the hay".
If a woman told me she was going to bunk out or hit the sack, it would merely sound very informal to my ears. I'm not saying that the words are not "ladylike", but they are simply more commonly heard among men than women. They are slang, not formal words.
Thomas/USA