Where do the six toenail ancestors come from?

"Who is the immigrant from the ancient locust tree? I took off my little toe to check the shape of my nails." This folk song is not only widely circulated, but also used as evidence by people to identify fellow villagers and the descendants of the ancient Sophora japonica immigrants. On trains, in hotels, in military barracks, in university dormitories, and even in foreign countries, when people from foreign lands gather together to inquire about their hometown or inquire about their ancestral home, it is common to see them take off their shoes, pull up their socks, and show their feet. Check to see if the nail on the little toe is deformed. If someone has a few vertical lines on his little fingernail, which looks like two nails, then his ancestors migrated from under the big locust tree in Hongdong. So they immediately recognized each other as descendants of Guhuai and regarded each other as fellow villagers of Hongdong. So they sat around and talked about the historical facts and anecdotes about the migration, and compared the rumors of their ancestors. They felt nostalgic for their homeland and missed their ancestors. "We are both immigrants from the ancient locust tree, and we are happy to meet each other after several lives." The cordial and friendly friendship is very strong.