The penis might also be referred to as the "vein" "(vena)", "tail" ("penis" or "cauda"), or "tendon" "(nervus)". The English word "penis" derives from "penis", which originally meant "tail" but in Classical Latin was used regularly as a "risqué colloquialism" for the male organ. Later, "penis" becomes the standard word in polite Latin, as used for example by the scholiast to Juvenal and by Arnobius, but did not pass into usage among the Romance languages. It was not a term used by medical writers, except for Marcellus of Bordeaux. In medieval Latin, a vogue for scholarly obscenity led to a perception of the dactyl, a metrical unit of verse represented as an image of the penis, with the long syllable "(longum)" the shaft and the two short syllables "(breves)" the testicles.