Why we go doolally

Someone who acts strangely or ‘goes mad’ is often described as having gone ‘doolally’. The military origin of this curious term is discussed in an aside in an academic article published in Twentieth Century British History.
The article discusses the changing concepts of how imprisonment during war impacts on soldiers’ mental health: POWs were originally thought to be immune to ‘war neurosis’ during World War I, but we now know that they are at high risk of developing mental illness.
However, there is a small but enlightening section that explains where the term ‘doolally’ comes from. Partly, it seems, from the experience of the troops in the British Empire and partly through bad spelling.

A link between captivity and mental illness in the armed forces had been established in the late Victorian period and was reflected in the term ‘doolally’, a popular term for madness. In 1861, the British Army had set up a base and sanatorium at Deolali, Maharashtra, about 100 miles north-east of Mumbai. It served as a transit camp for soldiers who had finished their tours of duty (‘time-expired’) and were waiting for a passage to Britain.
Troopships left Mumbai between November and March, so a soldier who completed his tour outside those dates often had a long wait for transport. Confined to a restricted life in camp during the hot summer months, so...