what is the difference among hole,pit and pit-hole?thanks
I just googled"dig a hole"or "dig a pit" but found the pics are similar, in some rural area,people would hoard potatos or other vegetables underground, they dig hole or pit or pithole?thanks

Question

Answer

The only thing that comes to mind is a clay pit. That is where clay is "mined" from. There almost seems to be a mineral or resource connection to many uses of pit. 
In general useage, one generally hears "dig a hole" more often than "dig a pit"
In the Old Testament, when a Prophet was thrown into a pit or dry well it was a repository for trash, chamber pot wastes, etc. So they were thrown into a really nasty place.

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