What does "vireo" mean?

Vireo: Any one of numerous species of American singing birds belonging to Vireo and allied genera of the family Vireonidæ. In many of the species the back is greenish, or olive-colored. Called also greenlet. Note: In the Eastern United States the most common species are the white-eyed vireo (Vireo Noveboracensis), the redeyed vireo (V. olivaceus), the blue-headed, or solitary, vireo (V. solitarius), the warbling vireo (V. gilvus), and the yellow-throated vireo (V. flavifrons). All these are noted for the sweetness of their songs.