rare = "obol".
2(In form Obolus) a genus of fossil brachiopods having a smooth orbicular shell, widespread in Cambrian and Ordovician rocks; (also obolus) a brachiopod of this genus.
Valid publication of the genus name: C. E. Eichwald Zoologia Specialis (1829) I. 274.
Late Middle English (in an earlier sense). From classical Latin obolus an obol, a small weight (Pliny and Celsus, a medical writer), in post-classical Latin also halfpenny (frequently in British sources 1086–1534), apothecaries' weight from ancient Greek (Attic) ὀβολός an obol, in Hellenistic Greek also a small weight (Galen) from ὀβελός, with vowel assimilation.