Why would sharding and hash be difficult to translate when they use metaphors that are easy to visualize in a "physical" context ?

I think the words' metaphorical meanings don't help much unless you already know what they mean. If you heard the word "sharding" for the first time and all you knew was that it had something to do with computers, I think you'd have a hard time guessing that it means "partitioning rows of a database across multiple servers to reduce load".