It seems that both the underdog and top dog terms originated from dog fighting which went on in the 19th century. The losing dog ended up on the bottom, or under the winner, who was on top. Hence we refer to the underdog as the person ( or team) in a competition who seems least likely to succeed or win, and top dog as the best, or the one expected to win.
To add an interesting fact, the word “bulldog” comes from the fact that dogs used to fight bulls along with the bullfighters.
About 10 years ago I took my boys to see Underdog, an American family superhero comedy film based on the 1969s cartoon series of the same name. Going to see kids movies with my boys is one of many things that I miss now they are adults. They loved going to the movies and for a time one would always declare after seeing a new one “that was the best film ever!” He has become far more discerning as he has grown older and is currently studying film and journalism at uni. He has a large selection of Blu Rays, including old classics and new, and I’m not going to be short of movies to watch when I’m laid up after knee surgery next week! We also had two movie dates last week when we saw Murder on the Orient Express, and Wonder, films we both really enjoyed…
“Be careful how you treat those who you perceive to be below you. The universe has a way of favouring the underdog.” – Curtis Tyrone Jones