In reply to:

And guess who the twins are that are capped with epididymides.


From http://www.bartleby.com/61/73/E0177300.htm:

Greek epididumis : epi-, epi- + didumoi, twins, testicles, pl. of didumos, double; see dwo- in Appendix I.

So, the epididymides sit "upon the twins." Quite pithy, although my favorite translation of anatomical Latin remains the august-sounding "foramen magnum," which in English is merely "big hole." "Dura mater" is a funny one, too. I think it must have been originally described by somebody who lived in the projects: "tough mother."