I was reading /u/yodatsracist's answer to an earlier question about Gypsies and he mentioned and linked to an article about the Yenish. The wiki article states that it has many Yiddesh words and through that also has Hebrew. What is the connection between Yenish and Yiddish?(besides that their names sound alike.)
There are three four things you should keep in mind:
Yiddish shares a lot of vocab with the Rhineland dialects of German and this does include such Aramaic words as Maloche, Kaschemme and Haberer. This is where the Yiddish language is from.
Martin Luther when writing his, influential for the modern literary German, translation of the bible avoided words he considered Jewish because he didn't like the Jews. So you while Jewish words are absent completely from the modern literary language they are dropped from time to time in medieval Minnesang and in later common speech.
The thief's cant in Germany, Rotwelsch, includes a lot of vocab from Yiddish along with words from the Roma language, Dutch, French and a clergyman's Hebrew and Greek. "Das Deutsche Gaunertum" is a book written by Friedrich Christian Ave-Lallemant, a 19th century police inspector, which includes a large rotwelsch glossary in the very end. You will see it's not plain Yiddish. In Yiddish you say "Yo" and "Nayn" for "Yes" and "No" and not the Hebrew "Ken" and "Lo" used in rotwelsch. And some of their Hebrew is not Ashkenazic either. They use "k" where in yiddish you'd have used a Scottish "ch". The author notes himself it is not Yiddish what they're speaking there. What was most exciting to me is that a lot of their vocab would be intelligible to the professional criminals speaking Fenya in modern Russia as well. It seems the thieves in Europe shared a lot of vocab but that's my original research.
Here you can read a book written by a Jenisch guy in the 19th century. He says they're not thieves but also craftsmen, musicians known mainly as thieves because the thieves are the only kinds of Jenischen you get bothered by as a common citizen. In the German wikipedia article on rotwelsch Jenisch is included as one of the dialects of rotwelsch along with languages spoken by different grouping of early modern craftsmen - they're listing tinkers, hawkers, rogues and merchants in different areas and eras. Looks it was not just a thieve's cant but more of general business cant.
Both were languages spoken by historically-marginalized peoples in Central and Southern Germany and Switzerland, who often led peripatetic existences and occupied economic niches that the dominant Catholic German population either couldn't or wouldn't do.
If you don't get an answer here*, you can also try /r/linguistics.
^^* ^^though ^^you ^^probably ^^will ^^since ^^we ^^have ^^some ^^people ^^(e.g. ^^/u/gingerkid1234) ^^who ^^are ^^pretty ^^knowledgable ^^on ^^the ^^relevant ^^topics
I've been summoned! I'm guessing what you're reading is this article yodats linked, which says:
The Yeniche vocabulary contains many words of Romani and Yiddish (and through this route, Hebrew) origin; it also has many unusual metaphors and metonomies that replace the standard German words.
Unfortunately the only source there is about a hundred years old and in German.
It's important to note that a lot of European languages have a significant number of Yiddish loanwords. Dutch is one example. So a central European jargon of sorts having a lot of Yiddish colloqiualisms isn't terribly surprising, since colloquial European languages in general do. Particularly in earlier times, when the Jewish population of Western Europe was much larger.
But part of it could be shared interaction from similar a similar economic and social role. Until the 1800s the European Jewish community was not well integrated into the local culture, still speaking Yiddish and still usually having required legal discrimination. Many Jews, like the Yeniche, traveled for work as merchants. This was a major economic niche for Jews more-or-less continuously in Western Europe. It would make sense for there to be more interaction between these groups than you might otherwise expect because of this.
It's also worth noting that the main sort of words being loaned would be Hebrew. Western Yiddish is mostly similar to High German, so most of the vocabulary would be shared with what Yenish speakers would use anyway, but with some shifts in sound and meaning. The largest source of foreign vocabulary in Yiddish is definitely Hebrew, so that'd be the main source of words. There's some Aramaic too, and a smattering of Judeo-Latin, which the wikipedia article mentioned as a contributor to Yenish, again without citation.
Unfortunately I know basically nothing about Yenish, only Yiddish, so hopefully someone will come along who does and I can fill in more of the Yiddish end of things.