I know this post is long dead but I felt I needed to put in the last word. :) Bob Miller's song "Hootenanny" is about an informal party with guests invited to perform songs. (This song was also released by Miller as "Jennie's Strawberry Festival".) It was included in Songs for Political Action because there is one line remarking on politicians.It was recorded in July of 1929 with his wife taking the part of "Jennie".
Curiously, there is a connection between Bob Miller and Pete Seeger. Pete was a member of the Almanac Singers, whose first publisher was ... Bob Miller. They were good friends as Bob had populists/left wing leanings and was very involved with the NY music scene through the 30's and 40's. So it's possible, though a stretch, that Pete heard the term hootenanny through Bob.
Bubba Miller, grand nephew of Bob Miller