Maybe it really is about house building, or, like many of the Grimms' stories, about principles so basic and timeless that they can only be expressed in parables. The Great Depression explanation was something I heard once about the Walt Disney Silly Symphony version of the story.
Yes, I think it's just meant as cute and childish. Compare Russell Brand's Booky Wook http://en.wikipedia.org/wiki/My_Booky_Wook, which suggests a small, insignificant, childish book.Erm ... I'm another who has never understood chinny-chin-chin to be anything other than [a cute version of the word] chin.