"Adj. Mad, crazy, insane. A shortening of doolally tap, a madness that afflicted British soldiers in Deolali, India. There's speculation as to whether the soldiers went mad whilst stationed there, awaiting the troop ship home, or that they were sent to the sanatorium there after going mad. Cf 'tapped'. Late 1800s" - peevish.co.uk
"Adj. Mad, crazy, insane. A shortening of doolally tap, a madness that afflicted British soldiers in Deolali, India. There's speculation as to whether the soldiers went mad whilst stationed there, awaiting the troop ship home, or that they were sent to the sanatorium there after going mad. Cf 'tapped'. Late 1800s"
- peevish.co.uk