Was Shylock a real name in use among Jews (or others) before Shakespeare wrote The Merchant of Venice? Or did Shakespeare invent the name?
Whether he invented it or chose it, he sure nailed it. I haven’t heard such a patently evil name since Beelzebub.
A quick internet search reveals nothing before Shakespeare. Most {“name origin” sites ignore it altogether (Who’d name their kid “Shylock”? It’s al;most like naming your kid “Darth Vader”), or simply dead-end at Shakespeare", like this one:
http://www.babynology.com/shakespearean_name-meaning_Shylock_m.html
It wouldn’t be unheard of to make up names. Heck, Dickens did it all the time. Prior to him, you never found names like “SCrooge” or “Pickwick”.
Since Shakespeare probably never met a Jew (they were banished from England in 1270 and weren’t allowed back for over 300 years), he would have no direct knowledge of Jewish names at all.
Inconclusive search here too, except learning that it probably wasn’t inspired by a real Jew that Willy knew, as they were banned from England in 1290, and not re-admitted until 40 yrs after his death (any he knew would have been hiding their Judaism).
Also learned that shyster is not an off-shoot, at least according to:
shyster. An unscrupulous lawyer (note that the definition presumes the
existence of scrupulous ones) . . .
The term does not come from—as suggested in various dictionaries—the
surname Scheuster, supposedly a lawyer noted for shyster-like practices; from
the name of the Shakespearean character, Shylock; . … or from any of the
various meanings of shy (e.g., to be shy of money). Rather . . . shyster evolved
from the underworld use of shiser, a worthless fellow, which derived in turn
from the German scheisse, excrement, via scheisser, an incompetent person
(specifically, one who cannot control his bodily functions) . . .
Hugh Rawson (1991)
A Dictionary of Invective
Perhaps not of contemporary Jewish names, but he would have read his Bible.
Damn you, RC, and your quick fingers.
scheisser 
Mrs. Piper and I went to the Globe in London earlier this year to see The Merchant of Venice. The programme said this about the name:
I was wondering if it was a misunderstanding of ‘side lock’ because of the Jewish prohibition on shaving sideburn hair, which grows long and curly if not trimmed. But if Shakespeare had never seen a practicing Jew, that seems unlikely.
It wouldn’t be the first time a person was named for a personal attribute.
Beelzebub is a variant of Baal Hadad, an ancient Semitic war/storm good, equivalent to Zeus. So, no eviler than Zeus.
Shakespeare may never have met a practising Jewish moneylender, but like anyone he knew of Dr. Lopez:
Shakespeare never went to Italy either, but his plays show a surprisingly deep knowledge of Italian culture and geography. He clearly knew how to do research (if not the bookish kind then by picking the brains of better-travelled friends) and so the fact that he never met a Jew hardly seems relevant.
They also show a lack of any deep knowledge of Italian culture and geography.
The gist of everything I have read is that he was well-read on the subject (for his time), but clearly had no personal experience, so the facts floated in a sea of assumptions and misimpressions. One would reasonably assume that he would similarly get a lot wrong about Jews.
It was my understanding that the ban on Jews was mostly observed in the breach: That is, there were plenty of Jews in London, and everyone knew who they were, and pretended they didn’t know… until one annoyed you in some way, or you owed him too much money, or whatever, and then you would suddenly be shocked to discover that he was a Jew, and he’d be kicked out of the country.
It’s not like the man wasn’t in the habit of inventing words.
That’s not to throw a punch at him. English is in the habit of inventing words left, right up and down.
I’m skeptical of lists like that. How do we know Shakespeare invented a word, just because we don’t happen to have a record of anyone using it before him?
Shakespeare’s reputation for inventing words is greatly exaggerated and overhyped. It is true that many words have their first known usage in Shakespeare’s works, but that doesn’t mean he necessarily coined them all. Much of it is likely due to his propensity to commit new terms from spoken language to writing and to the fact that Shakespeare’s works have been relatively well preserved compared to other written works of the same period. (And also, historically, the fact that the compilers of the Oxford English Dictionary—the first to systematically record diachronic word usages—started with Shakespeare and didn’t make a concerted effort to exhaustively check earlier sources. Nowadays, thanks to digitization, it’s getting easier to search for earlier usages. Many words once thought to have originated with Shakespeare have since been proven to have been used by others first.)
Though the name “Beelzebub” means “Lord of the Flies.”