E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
A John or Johnny Wilde is one who wears himself to skin and bone to add house to house and barn to barn. The tale is that John Wilde, of Rodenkerchen, in the isle of Rügen, found one day a glass slipper belonging to one of the hill-folks. Next day the little brownie, in the character of a merchant, came to redeem it, and John asked as the price that he should find a gold ducat in every furrow he ploughed. The bargain was concluded, and the avaricious hunks never ceased ploughing morning, noon, nor night, but died within twelve months from over-work. (Rügen tradition.)