Where does “ekster” come from?

ekster (Dutch) comes from Middle Dutch egestre, from Old Dutch agastra, from Proto-West Germanic agastrijā, from Proto-West Germanic ag-ad- ~ ag-at-, from Proto-West Germanic agu, from Proto-Germanic agō, from Proto-Indo-European h₂oḱ-éh₂, from Proto-Indo-European h₂eḱ- — sharp.

ekster (Dutch): Eurasian magpie, "Pica pica"; A magpie, any bird...