On Ms G's advice, I borrowed Born to Kvetch: Yiddish Language and Culture in All of its Moods by Michael Wex. It's a very entertaining and informative book - he goes into detail on the reasons behind the u/i variation in, for example, meshuge/meshige and kugl/kigl (in some words it originates in Hebrew and in others it comes from German). Early on he writes a sentence that struck me: "From a linguistic point of view, the Talmud is nothing less than Yiddish in utero" (page 15). He seems to be arguing that many Yiddish word and idioms reflect the Jewish worldview, that Yiddish arose "to give voice to a system of opposition and exclusion" (page 18). A simple example he gives is הײַנט haynt "today", which is derived from Middle High German heint "tonight" - "the Yiddish meaning depends on the notion of evening preceding morning, on the lunar calendar implied on the first page of Genesis and explain on the first page of the Talmud" (page 17).
Anyway, kvetch. קװעטשן kvetshn "press, squeeze, pinch, strain" is undoubtedly related to German quetschen "to squeeze" which was borrowed from Latin quatere "to shake" according to Grimm. Quatere is from Proto-Indo-European *kweh₁t- "to shake". In Greek, *kweh₁t- became πάσσω/παστός "to sprinkle". The derivative πασταί "barley porridge" was borrowed into Latin as pasta but with the meaning "small square piece of a medicinal preparation". This word became Italian pasta.
I've written about this root before, but I think the connection between kvetch and pasta is too cool not to mention.