The exact origins of Hammer Space (or hammerspace as it is commonly written) are not precisely known, though some well-founded theories have been offered over the years. The concept itself is widely attributed to the Golden Age of Animation, which began at the end of the 1920s with companies like Warner Bros. Animation, Hanna-Barbera, and Walt Disney Studios rising to prominence.
Hammer Space wasn't written as a distinct power until later on. Some fans attribute the first instances of characters actually pointing out their ability to produce objects from nowhere to Japanese animation and comics — it is also believed by some that this is where the term Hammer Space came from in the first place (likely from the community of fans). However, others believe that the role-playing game "Dungeons and Dragons" was the first to establish the convenient mechanic as an outright magical ability through the Bag of Holding — though, by that standard, it would arguably be more rightly attributed to the 1934 literature character Mary Poppins, who carries a carpetbag with seemingly infinite contents.
Regardless of where Hammer Space came from, it has long been a part of the Marvel Universe as an established superpower. Though its use is often in homage to animation, the narrative explanation for its existence is unique to the comics.
