There would have been little reason for Robinson to have avoided "dago." Possibly "Hash girl" is a typo (from a handwritten original) for "flash girl," but I'm just guessing wildly. "Flash girl" was probably printable anyway, though the elderly Robinson might have worried that it wasn't.

If it isn't a typo, there's no reason for Robinson to have written nonsense: he could just as well have written "Spanish," which scans better. So it's either a typo or something innocent that we're not familar with.

Where Robinson has "Hero bangidero," Hugill has "Heave-o, hang 'er hilo!" These could replace almost anything. Judging from some of Hugill's bowdlerizations, I'd say there's simply no way to conjure up the "real" words. Consider the related "Slav Ho"/"Saltpeter Shanty"; its structure and tune suggest the original words may have resembled those of "Three German Officers Crossed the Rhine," datable in one form or another to the 1830s.   

Robinson's lyrics may be almost completely bogus ("My Julia's beauty is rich and rare"? In a bawdy song?) and Hugill may simply have followed his lead. Nor is there any telling what Robinson in 1917 and Hugill's editors in 1961 may have thought "unprintable." Hugill had more latitude but not not much more.

FWIW, in Hugill's Sailortown (1967), "dago gals" becomes "dago whores," which is undoubtedly the original. "Heave-ho, hang 'er hilo!" becomes "Heave 'er, hang 'er, hilo!" Presumably the final syllable of the line really was "-o," as in a real Spanish word or a fake one. Beyond that, who knows?