you'd still expect the /r/ to remain, furthermore, in High
German this prototheme remains "Ebur" -
German Eber. Intervocalic /b/ in
Dutch and English became initially a bilabial fricative, then the easier labiodental fricative /v/ in OE written "f". In modern
German the bilabial fricative is an allophone of intervocalic /b/ in casual speech, but formally the regular stop.