Two Dogs Fucking

The youngest son of a great Indian chief went to his father and asked :
- Oh father, how did you choose the names for your three children ?
The great chief replied :
- My son, when your older brother was born, the first sight I saw after the moment of his birth was a bear running through the woods; so I named him Running-Bear.
The morning your sister was born, the first sight I saw was a beautiful star, so I named her Morning-Star.
But why do you ask me such a question, Two-Dogs-Fucking ?