Where does “yister” come from?

yister (Middle English) comes from Old English geostran, from Proto-Germanic gistr-, from Proto-Indo-European dʰǵʰyes-, from Proto-Indo-European dʰeǵʰ- — day.

Ancestry of “yister”, step by step

StepLanguageWordMeaning
1Old Englishgeostranyesterday
2Proto-Germanicgistr-yesterday
3Proto-Indo-Europeandʰǵʰyes-yesterday, the day before
4Proto-Indo-Europeandʰeǵʰ-day
Every word from Proto-Indo-European dʰeǵʰ- →Every word from Proto-Indo-European dʰǵʰyes- →Every word from Proto-Germanic gistr- →
yister — Etymology, Origin & Word History | Etymology Explorer