E. Cobham Brewer 18101897. Dictionary of Phrase and Fable. 1898.
Crank.
An Abram man (q.v.). So called from the German krank (sickly), whence cranky, idiotic, foolish, full of whims, and cranks (simulated sickness). These beggars were called cranks
because they pretended madness and sickness to excite compassion.