"you haven't shown bumpkiss."
I am not entirely sure, In referring to CombJelly's posts, but I think that is a "double negative", and therefore grammatically incorrect.
I think it should be "you have shown bumpkiss" or "you haven't shown lack of bumpkiss"......
But, perhaps I have drifted from my mark. Oh, and by the way, it is, more correctly, "bupkes".
Oh, and lest I forget, Etymologically speaking, "Bubkes" is a noun plural, but singular in construction and is probably derived from Low German, and is probably short for "kozebubkes", literally, goat droppings.
Hope this helps.
I know you would want to know this, because often, CombJelly has indicated in the past that he has had years of experience in this area.