Columbinitis

[Douglas G. Wilson]

>One of my favorite all-time bizarre plurals is arthritides for arthritis.

There are a large number of Greco-Latin nouns (mostly 'medical', I think)
pluralized like this.

There is an anatomical structure called the epididymis. It is paired, and
the plural is 'epididymides'. This seems to me like a sort of tongue-twister.

The epididymis is most often of interest when it becomes inflamed, and of
course this condition is epididymitis. The plural (which I don't remember
encountering but which might readily occur in the same kind of context as
'arthritides') would be 'epididymitides'.

-- Doug Wilson