why in samhill was the hill named after sam??

Sam Hill was an actual person, he was an activist who from the Pacific Northwest who in the early 20th century pushed for paved roads. He became well known and his name became a euphemism for the slightly offensive word “hell”.

I could be mistaken, but I think that "Sam Hill's" is a bowdlerised pronunciation of "Seven Hell's."

They couldn’t find Sam’s 👢 👢 so they couldn’t call it Boot Hill.