Green’s Dictionary of Slang

(orig. milit.) be off! go away!

1915		C.E.W. Bean Anzac Book 135/2: [Note] Imshee is the Arabic for ‘go away.’ The Australian Corps, which had so far employed it only to street hawkers in Cairo, used this war cry on April 25. – Eds.
1917		C. Sommers Temporary Crusaders 23 Dec. 🌐 I’m getting quite a vocabulary now [...] ‘Imshi Yalah’ means that you no longer require the presence of an importunate orange seller.
1918		R.H. Knyvett ‘Over There’ with the Australians 80: The first Egyptian word we learned was ‘Imshi!’ literally, ‘Get!’ – but it generally required the backing of a military boot to make it effective.
1925		(con. WWI) Fraser & Gibbons Soldier and Sailor Words 127: Imshi: (Arabic). Go away. be off.
1930		(con. 1914–18) Brophy & Partridge Songs and Sl. of the British Soldier 131: Imshi. — Go! Away with you.
1937		Sun. Times (Perth) 4 July 8s/3: Myself and my colleagues of slangdom will now ‘Nick off,’ ‘Impshi!’ and ‘Do a get’.
1944		G. Blake Shipbuilders (1954) 60: ‘And thon camels!’ Danny capped him. ‘Imshi! Ee-e-cht! Remember the bastards?’.
1963		C. Wood ‘Prisoner and Escort’ in Cockade (1965) I ii: Ockie – on your feet imshi.
1977		(con. 1941) R. Beilby Gunner 174: Now, get moving! Imshie!