mamma san is term used endearingly for the old women who take care of the military boys on the tiny island of Okinawa. I'm sure it's not specific to only this one station in life but it's the one I'm most familiar with.
When I think of them, I think of skin tempered from a life that's been anything but easy but heavy crows feet from smiling anyway. Calloused hands from hard work but a gentle touch because there's not an ounce of malice in them.
Even though there was always a language barrier, they mothered us like doting hens. Mamma sans were the safest people on the island because they had platoons full of protective sons. If someone messed with mamma san they messed with the largest military power in the world.