Would you believe it?
A thagomizer (/ˈθæɡəmaɪzər/) is the distinctive arrangement of four spikes on the tails of stegosaurine dinosaurs. These spikes are believed to have been a defensive measure against predators.
The arrangement of spikes originally had no distinct name; cartoonist Gary Larson invented the name "thagomizer" in 1982 as a joke in his comic strip The Far Side, and it was gradually adopted as an informal term used within scientific circles, research, and education.