1885, "Two English Men of Letters" (uncredited), The Atlantic Monthly, Boston and New York: Houghton, Mifflin & Co., Volume 56, July, 1885, pp. 121-2, https://books.google.ca/books?id=8moCAAAAIAAJ&printsec=frontcover#v=onepage&q&f=false
He is concerned with his mental and spiritual growth, and so deeply interested in it is he that he is willing to spread upon the record the testimony of his memory to what can scarcely be regarded as less than donkeyish stupidity in youth.

The lion-skin had got pretty untidy already during Puzzle’s imprisonment in the stable and it had been knocked crooked during his journey through the dark wood. […] The head, besides being pushed sideways, had somehow got very far back so that anyone could now see his silly, gentle, donkeyish face gazing out of it.

I bounced my weight up and down, listening to the cheerful donkeyish heehawing of the floorboards.

Donkeyish

Meaning

Adj