Where does “Oostzaan” come from?

Oostzaan (English) comes from Dutch Oostzaan, from Dutch zaan, from Middle Dutch saen, from Old Dutch sān, from Proto-West Germanic sān(ō), from Proto-Germanic sēna, from Proto-Germanic *sa, from Proto-Austronesian *əsa.

Ancestry of “Oostzaan”, step by step

StepLanguageWordMeaning
1DutchOostzaan—
2Dutchzaansoon; cream
3Middle Dutchsaenquickly, soon; immediately, right away; suddenly,...
4Old Dutchsān—
5Proto-West Germanicsān(ō)immediately
6Proto-Germanicsēna—
7Proto-Germanic*sa—
8Proto-Austronesian*əsa—
9Proto-Oceanic*isa—
Every word from Proto-Oceanic *isa →Every word from Proto-Austronesian *əsa →Every word from Proto-Germanic *sa →