Cathay - Better known as William Cathay in order to fight as a soldier, the woman named Cathay Williams was the first African American woman to enlist in the military. Her name sounds a bit like Kathy, making it familiar, yet Marco Polo used it to refer to China.
Belle - Sojourner Truth, defender of women's rights, was born Isabella Baumfree and called Belle. Belle is not in the top 1000. Sojourner helped recruit African American troops for the Union during the Civil War.
Poppy - Not only do we wear poppies on Remembrance Day thanks to the poem "In Flanders Fields," but a poet named Moina Michael also wrote a poem in which poppies symbolized the blood of heroes.
Araminta - Harriet Tubman was born Araminta and known as Minty (and while Minty may not make the best nickname today, Minna, Minta, or even Ana might). The Underground Railroad is one of the most famous parts of the Civil War.
Hattie and Harriet, for the same reasons above.
Jeb - Jeb Stuart, aka James Ewell Brown. His most famous campaign was Gettysburg.
Birkett - Birkett Davenport Fry was a Confederate general in the Civil War, and was also an adventurer, lawyer and cotton manufacturer.
Fentress - An intriguing name, Fentress is a surname that means "adventurous." I have a love of most -tress names, although this one was found on Civil War general Thomas Fentress Toon. I think it would be lovely, feminine and unexpected on a girl.
Remember - as a middle name or a combo (such as Remember Joey, if that was the name of the person you wanted to remember) could work as a unisex name. On that note, Memory could also work.