Viridans streptococci

Etymology
viridans streptococci:

viridans: "green" (from latin vĭrĭdis, meaning "green")

streptos: "chain" (from greek στρεπτός, meaning "twisted", but used medically to refer to "chains")

coccos: "berry" (from greek κόκκος, meaning "berry")

Explanation
Viridans streptococci are a category of streptococcal bacteria, which have a tendency to be alpha-hemolytic (although some can be beta-hemolytic). Being streptococcal bacteria, their morphology is that of a chain (streptos) of berry-shaped cells (coccos). On blood agar (plates containing a mix of agar and blood), they tend to alpha-hemolyze, meaning they partially breakdown the red blood cells in the blood, resulting in a region on the plate which has a greenish colour (viridans). This is in contrast with beta-hemolytic cells, which fully breakdown those RBC, leaving no colour.

Synonyms
Streptococcus viridans

viridans streptococcal species