I think instead he's making a joke about locomotive engineers. Which is actually a good point, but marred by couple issues. First, the "engineer" is the perso

I think instead he's making a joke about locomotive engineers. Which is actually a good point, but marred by couple issues. First, the "engineer" is the person who drives the train, rather than the person feeding the fire. Second, the term is only frequently used in English speaking North America. Further description here: Why are US train drivers called engineers? https://www.bbc.com/news/blogs-magazine-monitor-32758223 https://www.bbc.com/news/blogs-magazine-monitor-32758223