Salmonella sounds like a fish disease, but it is a surname with a Latin ending added.
Daniel E. Salmon (1850 to 1914) was an American veterinary surgeon who led research at the USDA's Bureau of Animal Industry. In the 1880s the bureau was trying to find the cause of hog cholera, a deadly pig disease. Theobald Smith, a young researcher who had joined the bureau in 1883, isolated a bacterium from sick pigs in 1885. It was first called the hog-cholera bacillus.
Credit for the find has long been argued over. Salmon and Smith disagreed several times about who deserved how much. Encyclopedia.com says Salmon tried to claim credit for Smith's work, and the dispute helped push Smith to leave the bureau in 1895. NPR reports that many people believe Smith, the assistant, was the first to isolate it.
The name came later and from outside the lab. In 1900 Joseph Lignières, a French-born bacteriologist working in Argentina, proposed the genus name Salmonella in Salmon's honor. Etymonline calls it a Modern Latin coinage of 1900 and dates the word in English to 1913.
There is a further irony. Smith's bacillus turned out not to cause hog cholera at all. About twenty years after his find, the real cause was shown to be a virus, and the bacterium was recognized as a secondary invader. The organism became the prototype of the genus, even though it was found while chasing the wrong cause of the disease.
The story is a standard example of an eponym that honors a supervisor. Several other bacteria carry the names of researchers in the same way.