Having played around with various ways of carrying kit that didn't involve a bag, I reckon that a 'possibles pouch' is something that probably would have been used by a lot of people.
If you camp with your equipment wrapped in a bedroll, rather than in a bag, then stopping to get access to stuff is difficult - this is where having a small separate bag for things you need 'on the move' is important - be it either a belt-pack or a shoulder-bag. Your bedroll of course contains al the things you need to set up camp.
Small woven or leather bags, either for the shoulder or worn on a belt or rope around the waist are prevalent in Native American culture, and it is likely that these would have been picked up by travellers moving through these countries.