Sarah is a traditional name, Governor Palin's husband's name is Todd, which isn't that unusual, so how did they come to choose their children's names? The boys are Track and Trig, and the girls are Bristol, Willow and Piper.
In an interview in the US People magazine (http://www.people.com/people/article/0,,20222685_2,00.html) Todd Palin says that the name Track was chosen because their families were all keen athletes. I thought at first that perhaps the baby's name Trig was short for trigger - Sarah Palin is keen on shooting, I believe - but Todd Palin says trig is a Norse word meaning 'strength'.
I suspect the names all have Alaskan links. I read somewhere else that there is a great uncle Trig, who is a fisherman, and baby Trig's middle name, Paxson, is the name of a tiny Alaskan community. Willow and Bristol Bay are places in Alaska, too. In the People interview, Todd Palin says of Piper, that it is a cool name. It's not that rare, and was in the list of top 250 girls' names in the USA in 2006. That might have something to do with the fact that Piper is one of the sisters in the television series Charmed. I note also that Willow is a character in another popular TV show, Buffy the Vampire Slayer. I can't believe that Sarah Palin named her daughters after television characters. Surely, with her busy life, she can't have time to watch TV too!