For a 19th century Rocky Mountain explorer, every mountain, hill river and lake encountered was a blank slate. (They had Native American names, sure, but nobody cared about those.) Most prominent features were named after royalty, dignitaries, or family or friends of the explorers; some were named based on their appearance (such as Castle Mountain); and some got really weird names. In 1858, a pack horse owned by explorer James Hector fell into this river. In trying to get the horse out of the water, Hector was kicked in the chest, and so the Kicking Horse River was named. :)