Mere-grota

According to the Old English Dictionary:

an;

mere-grota

m. A pearl :-- Meregrota margarita, Wrt. Voc. i. 85, 24. On ðám beóþ oft gemétte ða betstan meregrotan quibus inclusam sæpe margaritam optimam inveniunt, Bd. 1, 1; S. 473, 18. [Cf. O. Sax. meri-grita, -griota.] mere-grota