background, not depth:

Foetor is the Latin spelling; it was plain old "fetor" in 1962 in NYC and it meant simply "a bad recognizable smell." It's more akin to "fetid" than to "fell," I suspect, though perhaps there is a common origin.

Specifically there was "fetor hepaticus," the characteristic smell of patients with liver failure, described as being like spoiled hay. Those patients often had high levels of ammonia (ordinarily detoxified by the liver, but not in these unfortunates) which may have been a, if not the, major contributor.

Diabetes out of control (keto-acidosis) also has a recognizable odor: fruity, sweet breath. I don't recall that it has its own name, though -- "fetor diabeticorum" or some such?

Bill? Doc?

P.S."Virus" is the root of "virulent". But just how do both of these relate to latin "vir" = "man" ?