An oft-repeated false etymology claims that the name comes from a contraction of Fat Man and Little Boy, the atomic bombs dropped on Japan during WWII, as a symbolic insult to Japanese motorcycles.

[6][5] In a 2015 interview, Scott Miller, Harley-Davidson's vice president of styling and product development, confirmed that the name was simply descriptive and had nothing to do with Harley's Japanese competitors.

The 2018 Softail frame has a modified swingarm with a Showa rear monoshock suspension mounted beneath the seat, replacing earlier twin shocks.

So as to provide a more comfortable and better controlled ride with improved handling, the front forks contain a Showa "Dual Bending Valve" (SDBV),[13] a cartridge simulator using two valves to control compression and rebound damping, giving linear damping characteristics proportional to fork stroke speed.

[3] The Fat Boy earned a place in American pop culture after appearances in the movie Terminator 2: Judgment Day.