I didn't know this either. The main thing I knew about them was that they were from South Africa, and so I think it's also interesting that they used the title of a 1942 movie (which I don't think would have been well-known even back then) for their group name. On top of that, Wikipedia states that they also didn't have a woman in the group originally, and that they only switched to using that name after adding her -- after having previously been known as The Zombies, which obviously would have caused problems once "Master Jack" became popular. Then I also had a look at the article about "Master Jack", where I found that the song was written by someone who wasn't a member of the group -- and re the title of the song, it quotes lead vocalist Glenys Lynne as saying: "In certain mines the foreman is called 'Master Jack', and the song tells the story of a labourer who works diligently for this master for years and years and then decides to go out on his own and exercise his desires and aspirations as an individual to be something other than a labourer." I had always figured that the song title and the group name were linked in some way, so all of this came as a surprise to me as well.