etymological question: "jack shit"

[Mark A. Mandel]

My daughter Susannah asks the following. I have looked in the archives to
no avail.

>>>>>
some friends of mine are having an argument about the
etymological origins of "jack," when used as in "he doesn't know
jack."  others point out the similarity of this construction to
"jack shit," when used to mean "nothing" -- in fact, you can also
say "he don't know jack shit."

the question is, where and how did this originate?

i thought some of your dialectologists might know. :)
<<<<<

-- Mark A. Mandel