Even though The Lord of the Rings is usually referred to as a trilogy (as there are three books and three movies), its actual intention when published was a little different. Lord of the Rings is actually technically one novel split into three books, with each of those books also being split into two parts within the pages as well. Tolkien originally wanted to publish the whole thing as one novel, but it was split into three to save on paper costs (and this was probably lucky for fans as well, as it makes the process of reading the series more manageable).
The titles of all three parts of LOTR also carry great meaning to the story. The Fellowship of the Ring is clearly in reference to the group that forms around Frodo as he embarks on the quest to take the One Ring to Mordor, and the bond shared by these characters is integral to the story as a whole. The Return of the King refers to Aragorn's rightful return to the throne of Gondor, which is also an important thread that the whole story follows. The Two Towers, however, seems like a bit more of a vague title, as while there are towers in the book, it's not like the story solely focuses on those structures. What are these two towers, and why are they so important to The Lord of the Rings?
What Are The Two Towers Called?
The most important question to answer right off the bat is this: which two towers is the title referring to? The heroes come across many towers over the course of the series, so which two in particular are the ones that Tolkien wanted to take special note of? Well, as is the case with a lot of Tolkien's lore, even he himself wasn't exactly sure for the longest time. Even though one would think that the man who came up with the title would know which towers he was referring to, but he actually waffled on the answer for quite a while. To be fair, he never intended for the work to be split into three volumes, and he actually had quite a bit of trouble coming up with the title for the middle book.
It initially seemed as though he was trying to decide between three different options that he thought were important to the story in some way. One combination was the Orthanc (Saruman's tower) and Barad-dûr (Sauron's tower), another was Minas Tirith and Barad-dûr, and the final option he considered was the Orthanc and the tower of Cirith Ungol. However, after all of that, he eventually settled on the decision that it was actually none of these combinations, and that the "two towers" in question were actually in reference to the Orthanc and Minas Morgul.
What Is The Significance of the Two Towers?
Minas Morgul definitely seems like a strange decision to come to, as the other locations are much more obviously important to the story. The Orthanc, for instance, is Saruman's stronghold, and he plays a major role in th story as one of the main antagonists of The Two Towers. His rise to power and corruption by Sauron is integral to the story, with the Ents defeating Saruman's troops and destroying Isengard (as well as the Battle at Helm's Deep involving Saruman's army) being massive beats of the story. The Orthanc makes sense as an important location in that second part of LOTR, but the same can't exactly be said for Minas Morgul.
Minas Morgul used to be a city that belonged to Gondor, but was taken over and became the fortress for the Witch-king of Angmar - yes, the leader of the Nazgûl that Eowyn eventually stabs in the face. There are probably some fans who won't even really remember this location, which is understandable as it appears in exactly one scene in The Two Towers. Frodo and Sam come across Minas Morgul on their way to Mordor and watch as the Witch-king leads his armies out of it to go to the Battle of Pelennor Fields. In the movie adaptations, Minas Morgul doesn't even appear until the third film because of the way the timeline of events was translated to the screen.
So why exactly did Tolkien choose Minas Morgul as the second titular tower? As is the case with many of Tolkien's decisions that never got fully explained, no one really knows. A lot of fans agree that there are other towers that would have made sense, specifically Cirith Ungol, which is where the Orcs take Frodo after his encounter with Shelob and where the book ends, or Barad-dûr, which would be a good pairing with the Orthanc as the other stronghold of evil in the story. However, Tolkien struggled so much to come up with an explanation for the title that he never fully expanded on why Minas Morgul was his final choice. It seems to simply be one of those pieces of Tolkien's lore that fans can speculate on, but will never know the full answer for sure.