Try these two sources - "The Land Where the Blues Began" by Alan Lomax Jr. This is a wonderful history of the roots of the blues. It explains much of the jargon used in old blues. Sorry I don't have the publisher's info handy right now.
- "Robert Johnson - At the Crossroads- The Authoritative Guitar Transcriptions" Transcribed by Scott Ainslie and Dave Whitehill, Published by Hal Leonard Publishing Co. , 1992,ISBN 0-7935-1093-7 This is mainly guitar tab and lyrics, but defines a lot of the terms.