Just as an additional fragment of information to this writeup (oh good noders, let me
ride the coattails of greatness), I will say that:
Signior is an antiquated spelling of what is currently written signor, an apocope of signore, meaning "sir".
Signor/Signore, currently the standard formal title proper for all Italian men (excepting the Dottore, of course), formerly was only applied to men of good birth, much like "sir".
The world cazzo is a vulgar but very common term for penis, roughly equivalent to "cock". Hence, the understandable ire of Captain Cazzo/Captain Cock.