The story
- Proto-West Germanic · inherited from*-astrijā
- Old English · inherited from-estre“-ster”
- Middle English · inherited from-estere
- English today-ster
From Middle English -estere, -ester, from Old English -estre (“-ster”, feminine agent suffix), from Proto-West Germanic *-astrijā, of disputed origin. Cognate with Middle Low German -ester, Dutch -ster.
Etymology from Wiktionary, CC BY-SA 4.0.