Solo: A Star Wars Story is great at referring back to the original trilogy, prequels, and Expanded Universe in subtle ways. Objects lurking in the background, offhand remarks made at a Sabaac table, and seemingly insignificant actions (i.e. Han shooting Beckett first) all come together to enrich our understanding and love for the galaxy far, far away.
One such Easter egg (if you even wanna call it that) is so tiny, that you'd never know it was there without the tie-in book Solo: A Star Wars Story The Official Guide by Lucasfilm Story Group member Pablo Hidalgo. Also the author of the Last Jedi's Visual Dictionary, Hidalgo provides an in-depth examination of all the wide variety of characters, weapons, uniforms, ships, planets, and aliens that make up each frame of Solo.
Pages 16-17 are devoted to Han and according to Page 17 in particular, his brown jacket that he wears for most of the movie is made from Nerf-leather. Why is that significant? Well, you'll have to go back to 1980 and the release of Empire Strikes Back. While in the Rebel base on Hoth, Han (Harrison Ford) and Leia (Carrie Fisher) get into a bit of a tiff, which culminates in the Alderaanian princess saying:
"Why, you stuck-up, half-witted, scruffy-looking nerf herder!"
Over the years, the insult has become an inexorable part of the smuggler known as Han Solo and the fact that the makers behind Solo decided to give a little nod to Leia's infamous bit of dialogue shows just how much they care about this universe and its fans. After all, Lawrence Kasdan helped write the screenplays for both Empire and Solo.
But what are Nerfs and those who herd them? No, they're not foam darts that young kids shoot at each other. Nerfs were actually cow-like animals, which are raised for their hides, milk, and meat. Like the Earth-bound bovine, beasts were important livestock on several worlds, including Alderaan, which explains why Leia knew the term "Nerf-herder."
Despite their many uses, people steer clear of Nerfs due to the foul odor they give off. To make them an even more disgusting animal, mucus begins to spew from their noses and mouths when they're frightened. Nerfs were also used by the Empire in keeping the grass nice and clean on Arkanis, the planet, which houses the Imperial Training Academy. During the time of the Rebellion, Han and Luke transported a group of female Nerfs to the famine-suffering planet of Ibaar.