Do you have to be of Native American ancestry to name your child Seneca, or any other Native American baby name? Personally, I don't think so. In my opinion, since we live in the United States, which was originally just Native American land, it honors our ancient country.
Seneca, unisex, is the name of a Native American tribe that is part of the Iroquois Confederacy, and today's Iroquois League was also known as the Five Nations or the Six Nations. The Seneca tribe lived furthest west. Their name is Onöndowága, meaning "People of the Great Hill."
It is only by coincidence, but Seneca was also the name of a Roman philosopher and statesman, tutor and advisor of the emperor Nero, who lived B.C. and wrote Oedipus. In Latin, Seneca means "old." Those named Seneca could be in reference to either the statesman or tribe.
Heavyweight boxing champ Floyd Patterson named his daughter Seneca after the name of the street he was on while trying to think of a good name.
And then there is Seneca Falls, New York, the place of the Seneca Falls Convention for women's rights.
In 2010 there were 26 baby boys named Seneca and 30 baby girls. In 2011 there were 16 boys and 29 girls named Seneca.