These are called "idioms", expressions that are peculiar to a particular language because they don't mean what they mean, so to speak.

I remember being rather amused when I was learning German, reading that someone went to see Herr Professor Schmidt, and asked the maid to see him.

She replied, "Es tut mir leid, er is nicht zu hause."

Transliterated, this would be, "It does me heavy, he is not home."

Dave Oesterreich