It's a myth that most enslaved blacks bore the last name of their owner. Only a handful of George Washington's hundreds of slaves did, for example, and he recorded most as having just a first name, says Mary Thompson, the historian at Mount Vernon.
Still, historian Henry Wiencek says many enslaved blacks had surnames that went unrecorded or were kept secret. Some chose names as a mark of community identity, he says, and that community could be the plantation of a current or recent owner.
"Keep in mind that after the Civil War, many of the big planters continued to be extremely powerful figures in their regions, so there was an advantage for a freed person to keep a link to a leading white family," says Wiencek, author of "An Imperfect God: George Washington, His Slaves, and the Creation of America."
Sometimes blacks used the surname of the owner of their oldest known ancestor as a way to maintain their identity. Melvin Patrick Ely, a College of William and Mary professor who studies the history of blacks in the South, says some West African cultures placed high value on ancestral villages, and the American equivalent was the plantation where one's ancestors had toiled.
Last names also could have been plucked out of thin air. Booker T. Washington, one of the most famous blacks of the post-slavery period, apparently had two of those.
He was a boy when Emancipation freed him from a Virginia plantation. After enrolling in school, he noticed other children had last names, while the only thing he had ever been called was Booker.
"So, when the teacher asked me what my full name was, I calmly told him, 'Booker Washington,"' he wrote in his autobiography, "Up from Slavery." Later in life, he found out that his mother had named him "Booker Taliaferro" at birth, so he added a middle name.
He gives no indication why the name Washington popped into his head. But George Washington, dead for only 60-odd years, had immense fame and respect at the time. His will had been widely published in pamphlet form, and it was well known that he had freed his slaves, Thompson says.
Did enslaved people feel inspired by Washington and take his name in tribute, or were they seeking some benefits from the association? Did newly freed people take the name as a mark of devotion to their country?
"We just don't know," Weincek says.
But the connection is too strong for some to ignore.
"There was a lot more consciousness and pride in American history among African-Americans and enslaved African-Americans than a lot of people give them credit for. They had a very strong sense of politics and history," says Adam Goodheart, a professor at Washington College and author of the forthcoming "1861: Civil War Awakening."
"They were thinking about how they could be Americans," Goodheart says. "That they would embrace the name of this person who was an imperfect hero shows there was a certain understanding of this country as an imperfect place, an imperfect experiment, and a willingness to embrace that tradition of liberty with all its contradictions."
Many black people took new names after the Revolutionary War, the Civil War, and the black power movement, says Ira Berlin, a University of Maryland history professor who has written books on the history of African-Americans.
"Names are this central way we think about ourselves," Berlin says. "Whenever we have these kinds of emancipatory moments, suddenly people can reinvent themselves, rethink themselves new, distinguish themselves from a past where they were denigrated and abused. New names are one of the ways they do it."
But for black people who chose the name Washington, it's rarely certain precisely why.
"It's an assumption that the surname is tied to George," says Tony Burroughs, an expert on black genealogy, who says 82 to 94 percent of all Washingtons listed in the 1880 to 1930 censuses were black.
"There is no direct evidence," he says. "As far as I'm concerned it's a coincidence."