Definition of "blimy"

Blimy if I don't believe 'e's taking 'ome 'is washing up his back.

1908 September, Jerome K[lapka] Jerome, “Passing of the Third Floor Back”, in Passing of the Third Floor Back, New York, N.Y.: Dodd, Mead and Company, page 2

‘Blimy, Will,’ he said confidentially.

1988, Alan Hollinghurst, The Swimming-Pool Library, paperback edition, London: Penguin Books