I've often wondered about the etymology of 'shyster.' From German scheissen, to shit? That would fit well with the old joke, "What is the difference between a lawyer and a bucket of shit?' "The bucket." I am also put in mind of scheusslich: hideous, atrocious, abominable. Turning to the 'shyster' entry in my Webster's, I read, "prob. fr. Scheuster fl. 1840 Am. attorney frequently rebuked in a New York court for pettifoggery."
According to Robert Hendrickson, Encyclopedia of Word and Phrase Origins, p. 659:
Shyster, an American slang term for a shady disreputable lawyer, is first recorded in 1846. Various authorities list a real New York advocate as a possible source, but this theory has been disproved by Professor Gerald L. Cohen of the University of Missouri-Rolla, whose long paper on the etymology I had the pleasure of reading. Shakespeare's moneylender Shylock has also been suggested, as has a racetrack form of the word shy, i.e., to be shy money when betting. Some authorities trace shyster to the German Scheisse, "excrement," possibly through the word shicir, "a worthless person," but there is no absolute proof for any theory.
A little further research reveals that Professor Cohen's "long paper" is in fact a short book of 124 pages published in 1982 by Verlag Peter Lang. See here for a review. Cohen argues that the eponymous derivation from 'Scheuster' that I just cited from Webster's is a pseudo-etymology. 'Shyster' no more derives from 'Scheuster' than 'condom' from the fictious Dr. Condom. Nor does it come from 'Shylock.' It turns out my hunch was right. 'Shyster' is from the German Scheisser, one who defecates.
The estimable and erudite Dr. Michael Gilleland, self-styled antediluvian, bibliomaniac, and curmudgeon, who possesses an uncommonly lively interest in matters scatological, should find all of this interesting. I see that the Arizona State University library has a copy of Gerald Leonard Cohen's Origin of the Term "Shyster." Within a few days it should be in my hands.