"Hilo" in the Hawaiian Islands was quite a signifucant poort in tyen sufgar trade in the 19th century, and that's what would have been meant sometimes when the word crops up - eg "Johnny came down from Hilo".

But what looks like the same word needn't always mean the same thing - these songs weren't written down at the time. I suspect at times "Hilo" might actually have been "haul-o", marking the signal for a concerted heave.