"unscrupulous lawyer," 1843, U.S. slang, probably altered from German Scheisser "incompetent worthless person," from Scheisse "shit" (n.), from Old High German skizzan "to defecate" (see shit (v.)).
[origin unknown and hotly disputed; perhaps fr the name of a Mr Sheuster, a New York City lawyer of the early 1800s; perhaps fr German Scheisse, ''shit,'' or Scheisser, ''shitter,'' by way of anglicized forms shice and shicer attested fr the mid-1800s, with the addition of the agentive suffix -ster; perhaps because prisoners were said and advised to fight shy of, ''avoid,'' lawyers who frequented jails, esp the Tombs in New York City; perhaps fr earlier sense of shy, ''disreputable, not quite honest,'' and -ster]