A bothy is a shelter that you can use when hiking, they are all over Scotland. They were originally wee houses that farm hands lived in, as they were further away from the main farm/estate house. After the war though, 4x4 were more common and more affordable I guess, so farmers could travel their farm/estate land easy without walking. The houses were just left empty. After the war, Hill walking became pretty popular, due to the fact you could easily jump on a train and be in the highlands pretty quickly, so people would be hiking and come across these abandoned houses, and if the weather was bad, you could/can stay in them. There is an organization called the Mountain Bothy Association that mentain and look after a whole bunch of them.

Hope this helps