Not on the song specifically, but since this thread has come to include a discussion of code language I want to make a comment I believe I have made before in other threads-- but who knows where, now? ~:)

And that is, that code language could have been used not only about escapes-- I agree with Azizi's doubts about that-- but in communicating among slaves about day-to-day life. Not code for the purpose of fooling massa about escape plans, Capital C Code-- but veiled references to feelings and experiences of life as an owned, oppressed, grieving, angry human being. Small c "code."

It's my opinion that such would have served as a point of perceived commonality between slaves and the way unsaved folks were portrayed by religious imagery of the time. Slave songs (for that's what the authentic songs we now call spirituals are ) resonate with metaphors of captivity, just as many Bible passages recount previous historical captivities as well as the captivity of a soul in bondage to sin.

~Susan