Well, I didn't know that; and in fact, it is not quite right. The primary meaning of "fascinum" is "charm" or "spell"; the use of the word to mean the penis seems to be derivative of the fact that the word was also applied to a phallus-shaped charm that was used for warding off the evil eye. The English word "fascinate" clearly derives from the primary sense of "fascinare," which is "to cast a spell," and so has no direct reference to the penis.
"Fascist" comes from the Italian "fascio," which itself comes from the Latin "fascis," which means a bundle. Mussolini and Gentile introduced the term by reference to bundle of sticks that symbolized the authority of magistrates in ancient Rome, though they may also have had in mind the idea of people banding together. None of the dictionaries that I have looked at suggest a connection with the word "fascinum."
