Kwets is the Dutch name of a certain species of plumbs (Prunus domestica subsp. domestica); it is a slender dark blue frosted prune used for making jams and the distillation of slivovitsj.

The origin of Prunus domestica is not clear. For a long time people supposed it was the result of crossbreeding between (Prunus spinosa) and(Prunus cerasifera). This would have taken place by accident in the Kaukasus region, where both parent species grew.

kvetch is a Yiddish word. I know I have the habit of wanting to see connections where they ain't, but still I like to see this word having travelled from the Kaukasus into the wide wide world.

For a person who is always complaining we also refer to prunes.
In Dutch "Zuurpruim" - "sour prune" is the word for what is called here a "kvetch".

Image of kwets