This is a not-nice word for a tosser who’s not shy about stirring the pot to clean you out in court – a shameless heist. A shyster is not a Shylock; the latter is an abusive term for a moneylender and has racist overtones, but our word du jour is not related to it and has no racist history. It’s an abusive term for a pettifogger, a larcenous liar of a lawyer, senior partner in Dewy Cheetham & Howe. The American Heritage Dictionary points out that calling someone a shyster might be considered libellous, and I will add that if the person in question really is a shyster, you can count on being sued so hard you even lose your fillings.
So obviously this is the sort of person about whom people say rude, even vulgar, things. In English we might make reference to such a person’s parentage, illegitimate, canine, or otherwise; in German, they will declare that he defecates – er ist ein Scheisser. Odd, that, isn’t it, given that everyone does it now and again? But this type does it on you. And this German word, with its big [aI] diphthong so like the sound you make when you get your bill, was borrowed into English. The spelling was modified to something more English- or Dutch-looking (perhaps with an influence of Shylock, but that’s speculation), and the ending was changed to the English ster, which we see in such as seamster, brewster, and gamester – and also trickster, huckster, and gangster.
The word has its share of hissing voiceless fricatives, marked with those two snakelike s‘s, and it ends with the retroflex (in North America) /r/, a sound thought of as too low-grade to be held long in pretty song. And, like its object, this word often keeps disreputable company, hanging around with types such as two-bit, blowhard, snake-oil peddler, money-grubbing, low-life, charlatan, sleaze, and – cover your eyes – used-car dealer.