It was part of the song sung by Caesar's legions as they marched the triumph's in Rome in 47 BC.
I've seen it translated numerous ways, including: 'Men of Rome, keep close your consorts, here's a bald adulterer." They all essentially say the same thing, though.
Here is the song in the full context, though butchered to rhyme in English:
Gaul was brought to shame by Caesar:By King Nicomedes, he.
Here comes Caesar, wreathed in triumph For his Gallic victory!
Nicomedes wears no laurels Though the greatest of the three.
Home we bring our bald whoremonger; Romans, lock your wives away!
All the bags of gold you lent him Went his Gallic tarts to pay.
Basically, this was Caesar's adoring troops mocking him for the scandalous and rumored affair that he had had with King Nicomedes of Bythnia. Though never proven, Caesar's enemies took great delight in mocking him with it. But Caesar, probably in part because of this rumor from his youth, countered it by becoming a well known womanizer (not in a chauvinistic sense but as a seducer, especially of enemies wives and relatives). The song refers to both the rumor and Caesar's known behavior, and because it was his own men, Caesar apparantly did nothing to stop the song.