I always figured it meant some who was practical, friendly, hard-working and more than a little traditional but not necessarily harsh in their traditional mindedness.
My grandfather was something of a salt of the earth type with regards to my above description. He was a wealthy man but his daughters were all required to hold down jobs and do well in school. He also raised each of his daughters to be able to do anything he could do, and he was a tall, big, strong man. To this day, my teeny, chubby, 50 something, arthritic, cancer survivor mother can do more manual labor than most of the young, strong, healthy men I know. He was always kind and tried to make his judgments of people on an individual basis. He was traditional in that he had a hard time swallowing my mother having a child out of wedlock and, had he been alive, I’m sure he would have had an awful lot of trouble getting past my wild hair.
Please excuse my long answer. I take any excuse to talk about my grandfather that I can. :)