sh-l-m — to be whole, complete
ש.ל.ם (shalem) means whole, not calm. Shalom, paying a bill, finishing a task and the name Jerusalem all sit on this root.
The word family
Every word below is built on ש.ל.ם. Same three letters, different vowels and prefixes.
Paying is completing — you make the transaction whole.
The second half carries this root. The traditional reading is a city of wholeness.
What I tell students about this root
Shalom as a greeting is not wishing someone a quiet life. The root is completeness, so the question מַה שְׁלוֹמְךָ? (mah shlomkha?) literally asks what your wholeness is — how intact you are. That is a rather more searching "how are you" than the English one.