Kathleen,
I know this probably doesn't help much, but when I was in New Zeland I heard people referring to wild flowers that were blue in colour as blueys - regardless of ther type.
My point being, that it could mean anything really. I might stick with the roll sack. Isn't that what a swag is? That would seem to be the most reasonable meaning you have come across so far. "Humble" may also reffer to a sailors "meager" possesions. I do not believe they would have been allowed many items of their own on long voyages.
Best of luck,
Henry B.