Only Hardcore NCIS Fans Know This Fact About Gibbs's Name
Mark Harmon's filmography includes almost 40 years of acting work since he got his start in Hollywood. Before that even, Harmon was a prodigious college football player with enough talent to be scouted by the NFL. Despite such a long and multifaceted career, however, Harmon's starring role in NCIS overshadows virtually every other one of his undertakings and is likely to continue to do so, even if his rumored imminent departure ultimately comes to pass.
That's because Harmon has been at the center of NCIS over the course of its run of 18 seasons and counting across more than 400 episodes. Harmon, in fact, is credited in more episodes of the series than any of his co-stars, save for Ducky actor David McCallum. Given that NCIS is massively popular in addition to being formidable in length, it's unlikely that Harmon will ever star in a project of comparable magnitude, barring some sort of superhuman feat.
Even though Harmon has appeared in NCIS more times than most actors have appeared on TV, the origin of his character's name, Leroy Jethro Gibbs, is relegated to a single episode. Only hardcore fans and series completionists, therefore, know this key detail about the lead character in one of the longest running TV shows in history.
Leroy Jethro Gibbs is not the only Leroy Jethro in NCIS lore
The origin of Leroy Jethro Gibbs' name is revealed in season 10, episode 5, appropriately titled "The Namesake." While the episode features a requisite murder in its present that must be investigated by the Naval Criminal Investigative Service, a certain amount of its runtime is dedicated to Gibbs' past.
Gibbs' namesake is revealed to be a veteran of the Pacific Theater in World War II named Leroy Jethro Moore (portrayed by none other than Lando Calrissian actor Billy Dee Williams). He was a friend and business partner of Gibbs' father, Jackson Gibbs, back when they co-owned a general store in Stillwater, Pennsylvania. Though Jackson Gibbs and Leroy Jethro Moore met in a coal mine, Moore's time spent at war both inspired Jackson to name his son after his close friend and inspired Leroy Jethro Gibbs years later to enlist in the Marines himself.
Thus, while another series might feature such a backstory for its lead character early on or as a recurring source of motivation, NCIS' stoic Gibbs, rather, discusses this key component of his family history just once, leaving it for only the show's dedicated fans.