Where does “Rotterdam” come from?

Rotterdam derives from Middle Dutch rotterdam, composed of Middle Dutch dam and Old Dutch dam, ultimately from Proto-Germanic dammaz meaning a barrier across water.

Ancestry of “Rotterdam”, step by step

StepLanguageWordMeaning
1DutchRotterdam—
2Middle DutchrotterdamRotterdam
3Middle Dutchdam—
4Old Dutchdam—
5Proto-West Germanic*dammdam
6Proto-Germanicdammazdam
Every word from Proto-Germanic dammaz →Every word from Proto-West Germanic *damm →Every word from Old Dutch dam →