Skully is known by many names–the similar sounding variations generally vary by neighborhood, though I certainly heard “skelly” as well as “skully” in the Bronx. I think that the sing-song quality of “skelzee/skelzies” is extended from the original “skully/skelly” in much the same way as people shooting for the the 2-box would proclaim they were “going for twosies.”

As Snoop Dogg would say, “by any name, skelzizzle is off the hizzle for shizzle, dizzle.”