Western Washington has been invaded by a South American army ... of nutria (Myocastor coypus). Nutria are small (12- to 17-inch) semi-aquatic rodents which look like a beaver on steroids. Protectors of native species are organizing to repel the invasion. The nutrias' plan is to win by procreation (about sixty offspring per female per year).

The name of this wee beastie looks, for all the world, like a plural to me. The back formation of the singular would then be "nutrium" but that is unlikely. Where'd these critters get such a name?

singular: nutria; plural: nutrias

Etymology: Spanish, 19 C, from vulgar Latin, nutria, varient of lutra, meaning "otter".

The photographs in the newspaper looked a bit like otters, so one can see how the Spanish word might have been borrowed. It still ends funny.

There is a theory running around that the Latin first declension descended from an uncountable plural declension in an older language, hence its similarity to the second declension neuter plural. Or was it the other way round?

Well, Faldage, you otter know.

Bravo!