A lot vs. Alot: 9 Grammatical Pitfalls
(plural staphylococci), 1887, Modern Latin, the genus name, coined (on model of streptococcus) in 1882 by Scottish surgeon and bacteriologist Alexander Ogston (1844-1929), from Greek staphyle "bunch of grapes" (see staff (n.)) + Modern Latin coccus "spherical bacterium," from Greek kokkos "berry, grain" (see cocco-). So called because the bacteria usually bunch together in irregular masses.
staphylococcus staph·y·lo·coc·cus (stāf'ə-lō-kŏk'əs)
n. pl. staph·y·lo·coc·ci (-kŏk'sī, -kŏk'ī)
A spherical gram-positive parasitic bacterium of the genus Staphylococcus, usually occurring in clusters and causing boils, septicemia, and other infections.
Plural staphylococci (stāf'ə-lō-kŏk'sī, -kŏk'ī)
Any of various bacteria of the genus Staphylococcus that are gram-positive cocci and are normally found on the skin and mucous membranes of warm-blooded animals. Pathogenic strains such as S. aureus commonly cause infections of the skin, bones, lungs and other organs. Some staphylococcal disease, such as food poisoning, is caused by a toxin produced by the bacteria.