Cabin fever is an idiomatic term, first recorded in 1918, for a claustrophobic reaction that takes place when a person or group is isolated and/or shut in a small space, with nothing to do for an extended period. Cabin fever describes the extreme irritability and restlessness a person may feel in these situations.
A person may experience cabin fever in a situation such as being in a simple country vacation cottage. When experiencing cabin fever, a person may tend to sleep, have distrust of anyone they are with, and an urge to go outside even in the rain, snow, dark or hail. The phrase is also used humorously to indicate simple boredom from being home alone.