Balkan tap, n. — Green’s Dictionary of Slang

Balkan tap n.

[on pattern of doolally tap n.; proper name Balkans + tap, sunstroke; the term evolved to characterize the growing, happy indolence that took over men involved in the Macedonian campaign in WWI]

madness.

1919		H.C. Owen Salonica and After 57: ‘Balkan Tap’ is supposed to make you do all sorts of strange things.
1920		E. Alexander Powell New Frontiers of Freedom 243: I had observed that a profoundly pessimistic attitude of mind characterized all of the Americans or English whose duties had kept them in the Balkans for any length of time. In Salonika this mental condition was referred to as ‘the Balkan tap’ [...] and it usually implied that those suffering from the ailment had outstayed their period of usefulness and should be sent home.
1934		C.E. Vulliamy Fuslier Bluff 50: Perhaps a longer experience of Macedonia would have led to boredom or lethargy or to the mild imbecile condition known as ‘Balkan Tap’.
1940		(con. WWI) C.E. Vulliamy Calico Pie n.p.: A man suffering from Balkan Tap was [...] usually smiling, with a Lotus eater’s philosophy, and he was almost incapable of performing the most ordinary duties.
1976		(con. WWI) G. Nicol Uncle George 154: ‘Balkan tap’ [...] was democratically endured by many humble members of the British Salonika Forces.
2004–06		Omnificent Eng. Dict. in Limerick Form 🌐 Major Wilmer went barmy, poor chap, / And we all put it down to the clap. / But it seems the poor sod / Really thought he was God: / A bad case of the old Balkan tap.