Ostre

According to the Old English Dictionary:

an;

ostre

f. An oyster:--Ostre ostrea, Wrt. Voc. ii. 63, 71: i. 65, 67: ostrea vel ostreum, 77, 70. Ðonne cumaþ ða oftost of mettum and of cealdum drincan swá swá sindon cealde ostran and æpla, Lchdm. ii. 244, 2: Coll. Monast. Th. 24, 9. [From Latin.] ostre