The significance of "brought up in Venus' train" is unclear. The "train" may refer to Venus'ladies-in-waiting, in which case the phrase might indicate that Rynadine is accustomed to the company of beautiful women. How this would distinguish him from a rake is not immediately apparent. An alternate interpretation may refer to the Transit of Venus across the sun which occurred in the Victorian period, in 1874 and 1882, during when this song became popularized.
