Mr. Rushing, I spent some time trying to find this today (as did a couple of hard-working librarians in Memphis). Despite checking several slang dictionaries, what I found won't help much. But it repeats something I heard probably 25 years ago -- Rackensack may well be a near anagram:

http://listserv.linguistlist.org/cgi-bin/wa?A2=ind0202a&L=ads-l&P=1942

#>>...a few months ago in the "ozarks mountaineer" was the mention

> #>>that arkansas at one time was referred to as "rackensack" could you

> #>>please give details to this referral?...

>

> I know nothing about the name, but here's an unabashed WAG (wild-ass

> guess). It *looks* like a near-anagram of "Arkansas" :

> ARK-AN-SAS

> replace the 2nd S with a 2nd K and shuffle slightly

> RAK-AN-SAK

> -- which might have originated either as an actual

> misreading/misspeaking of the name or as a mock mistake of the kind a

> proverbial uneducated "hillbilly" might make. Again, this is pure

> uninformed speculation.

>

> -- Mark A. Mandel

> Linguist at Large