Here's what Todd Palin said about the names, while interviewed, of all of their children:
Where do your children's names come from? TODD: Sarah's parents were coaches and the whole family was involved in track and I was an athlete in high school, so with our first-born, I was, like, 'Track!' Bristol is named after Bristol Bay. That's where I grew up, that's where we commercial fish. Willow is a community there in Alaska. And then Piper, you know, there's just not too many Pipers out there and it's a cool name. And Trig is a Norse name for "strength."