Here are a couple of oddities
Frederick had a younger sister named Arianna, born around October 1822, four years after himself, two years after the sister between them, and three years before their youngest sister. He also had a cousin named Arianna, who was about a decade younger than his mother.*
In late 1826 or early 1827, Lucretia Auld gave birth to a little girl. The little girl was named Arianna.
Lucretia, as you may remember, was the daughter of Aaron Anthony, Frederick's first master, and the wife of Thomas Auld, Frederick's second master.
Slave babies sometimes received the names of members of the white family, but the reverse seems unusual. So, how to account for a baby in the white family being given the same name as a slave baby? A popular name? Since masters could exercise control of the naming of slave babies, was Arianna a favorite name of Anthony, so he gave the name to the eldest Arianna and his grandchild, with Frederick's sister being named for her cousin? Was this a name in the Skinner family -- the family of Anthony's wife -- that I have not yet discovered?
Both enslaved Ariannas appear on the Anthony inventory and division documents, the elder Arianna valued at $200 and the younger at $5. The other women of Arianna the elder's age received the same appraisal. Arianna the younger, however, was appraised $70 lower than two of other five year olds and $65 lower than yet another five-year old on the list, $25 lower than the two year-old boy and $20 lower than each of the two-year old girls, $15 lower than one of the one-year olds, and even $5 lower than her younger, one year old sister. In other words, what about her made her so unattractive to the appraisers and at such an early age?
In the division of the Anthony estate, the elder Arianna went to Richard Anthony and the younger Arianna went to Andrew Anthony, whom Frederick dreaded for his intemperance
*I'm actually uncertain of the exact relationship, and have to get back to the U.S. to look at the Dodge Collection with greater precision. Dickson Preston did not go that wide in his genealogy tables in Young Frederick Douglass. Right now, I think she was probably sister to Katy, the cook, since their parents comprised one of the two families included in Ann Skinner Anthony's dowry.