Capstan shanty. "O Sally Brown she promised me, a long time ago. She promised for to marry me, Way-ay roll and go." Combination of "Sally Brown" and "A Long Time Ago" with an entirely different tune.
Sharp seems to be the only source for this. Hugill classed it as separate from it relatives ("Sally Brown" and "Long Time Ago") though if it had to be declared one or the other, I'd put it with "Sally Brown" as they are both usually used as capstan shanties. - SL