Meaning

noun fertility goddess in ancient Greek mythology; wife of Cronus and mother of Zeus; identified with Roman Ops and Cybele of ancient Asia Minor

noun smaller of two tall fast-running flightless birds similar to ostriches but three-toed; found from Peru to Strait of Magellan

noun larger of two tall fast-running flightless birds similar to ostriches but three-toed; found from Brazil to Patagonia

originLearned borrowing from taxonomic name Rhea, from Ancient Greek Ῥέα (Rhéa, “the mother of Zeus in Greek mythology”).

Etymology from Wiktionary, CC BY-SA 3.0