It's trad. You'll find a great net hauling version of it by the Manhaden Chantymen, they also do "I'm Gonna Roll Here" another somewhat version of "Po' Laz'us". As a prison worksong it was recorded on "Negro Workaday Songs". If it's related to "I'm Gonna Roll Here" then it would also fall into a relationship with the 'BIG' prison songs "Berta" & "Ol Alabama" & is one of the few worksongs that are shared by singers in the prisons & on the sea. Barry