Definition of "unexpected"

She was a fat, round little woman, richly apparelled in velvet and lace, […]; and the way she laughed, cackling like a hen, the way she talked to the waiters and the maid, […]—all these unexpected phenomena impelled one to hysterical mirth, and made one class her with such immortally ludicrous types as Ally Sloper, the Widow Twankey, or Miss Moucher.

1918, W. B. Maxwell, chapter 2, in The Mirror and the Lamp‎

But the latest Santa Fe development, while not spurring the Rock Island to any further acceleration, has drawn fire from a totally unexpected quarter.

1940 May, “Overseas Railways: Acceleration Proceeds in U.S.A.”, in Railway Magazine, page 298

The windmill presented unexpected difficulties.

1945 August 17, George Orwell [pseudonym; Eric Arthur Blair], chapter 6, in Animal Farm […], London: Secker & Warburg