Bristol Bay and Willow are place and town names in Alaska. Piper, of course, is a plane. Don't know about Track, Trig-

Just Found This Explanation:

"Adedicated runner, she named her older son Track because he was born during that sport's season 18 years ago.

"Her youngest is 4-month-old Trig Paxson, whose first name is Norse for "true" or "strength" and whose middle name comes from one of his mother's favorite spots in Alaska.

"Her three daughters are Bristol, 17, Willow, 14, and Piper, 7.

"Palin said the eldest girl was named after Bristol Bay, where the family fishes.

"She hasn't explained the other girls' names, but there's a town in Alaska called Willow and Piper brings to mind the Piper Super Cub, a bush plane popular in her state."