„Guten Rutsch“‚ literally ‘A Good Slide’, is a common wish for New Year in #German. Since the 1950s it has been traced back to the Jewish New Year feast “Rosh Hashana” (‘head of the year’) but this is probably wrong - a thread (based on this article) https://www.juedische-allgemeine.de/kultur/rutsch-rosch-und-rausch-3/

2/ “Guten Rutsch” has probably been around since the early 1900s. The “Rosh Hashana” etymology was first proposed in 1956 by Siegmund A. Wolf in his “Wörterbuch des Rotwelschen”.

3/ #Rotwelsch is, broadly speaking, a German based language or sociolect used by vagrants and other travelling people as a kind of secret code. It is important here because many #Yiddish words found their way into Standard Germany via Rotwelsch
https://en.wikipedia.org/wiki/Rotwelsch 

4/ So according to the proposed etymology “Rosh” would have came into Standard German via Rotwelsch and somehow turned into “Rutsch”. The phonological reshaping would be caused by a folk etymological reinterpretation (a Yiddish word is replaced by a similar sounding German word).

5/ While this is not impossible the Hebrew/Yiddish etymology of “Rutsch” is now often refuted.
In West Yiddish, the Yiddish variety traditionally spoken spoken in Germany, “Rosh Hashana” is called “Rausch haschono/-ne” or “Rauschaschone/Rauschscheschone”.

6/ “Rausch” is also a word in Standard German meaning ecstasy (not the drug!) or intoxication. If West Yiddish “Rausch haschone” (etc.) was taken into Standard German, there would be no reason to change the word to “Rutsch”.

7/ “Guter Rausch” as a wish would make sense given the amount of alcohol usually drunken on New Year’s Eve.
I am not an expert but I am not fully convinced by this argument.

8/ Eastern Yiddish was also spoken in Germany around 1900 and there the holiday is called “rosheshone”. Further, the change to “Rutsch” may be due to dissimilation because it sounds like “Rausch”.

9/ I find another argument more convincing: the Yiddish pronunciations of “Rosh hashana” have never been a common New Year greeting in Germany. And why should you wish a good holiday that takes place in late summer on New Year’s Eve?

10/ The Grimmsche Wörterbuch (one of the earliest German dictionaries from the 19th century) and others mention that “Rutsch” can also mean “Reise” ‘travel’. “Guter Rutsch” would mean ‘good travel’ and to wish a good ‘travel’ into the new year is not too far off.

11/ Anyways – I’m wishing you all a good slide into 2021!
(See also: http://www.sprachlog.de/2008/01/01/hatten-sie-einen-guten-rutsch/)
#GutenRutsch