This comic is a reference to the sci-fi classic Star Wars. Obi-Wan Kenobi (on the left with the beard) and Luke Skywalker (who is on the left side of the table in the first frame) are trying to get off the planet Tatooine secretly and they enlist help from Han Solo and Chewbacca. Chewbacca is the very hairy one because he is a wookie from the planet Kashyyyk. Han Solo's ship is named the "Millennium Falcon".
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time. Randall (the author of the comic) wonders what Luke would say to Han if he had no idea what a falcon was. We as viewers accept it because of the etymology of the word in our world, but there is no evidence of a falcon in the Star Wars universe - especially for Luke who has been raised only on Tatooine, a desert world.
In the image text, Randall references the fact that Star Wars is set "a long time ago in a galaxy far, far away" and is curious how humans came to be in the Star Wars universe even though they (or we I guess) were not yet on Earth. The reference to Indo-European roots is another reference to etymology. As an example, certain words will have Indo-European roots because the word originated in Indo-European languages.
- [Obi-Wan Kenobi, Luke Skywalker, Han Solo, and Chewbacca are sitting in Chalmun's Spaceport Cantina, a wretched hive of scum and villainy.]
- Han Solo: Han Solo. I'm captain of the Millenium Falcon.
- Luke Skywalker: What's that?
- Han: It's the ship that made the Kessel Run in less than 12 Parsecs!
- Luke: No, what's a falcon?
- Han: ...