Indeed, in each novel in the trilogy, language is an important element. For example, in the first book in the series, Out of the Silent Planet, the hero, Edwin Ransom, is a described as a philologist--someone who specializes in the study of language (the more modern term would be linguist). Some believe that Ransom is in fact based on Lewis' good friend J.R.R. Tolkien, the beloved author of The Lord of the Rings and The Hobbit, who was an expert on Anglo-Saxon (the earliest form of English). Whether or not that is true, the fact that Ransom is a philologist plays an important role in the plot of Out of the Silent Planet, since it is due to his training as a philologist that he is able to learn the language spoken by the inhabitants of Mars after his arrival there. Moreover, in the second novel in the series, Perelandra, it is Ransom's mastery of that language, which Lewis later refers to as "Old Solar" (since it is supposedly spoken throughout the solar system) that enables Ransom to converse with the Green Lady, the "Eve" of Perelandra--the planet we know as Venus. Their conversations sometimes even touch on the subject of words and meaning.
However, it is in the third book of the trilogy, That Hideous Strength, in which language perhaps plays its biggest role. In the novel, both Ransom and his associates and their opponents, the evil scientists of the National Institute of Coordinated Experiments (NICE), are trying to locate Merlin, the celebrated magician of Arthurian legend. Merlin, they have discovered, is lying somewhere in a state of suspended animation under the woods belonging to the (fictional) University of Edgestow. A search party sent out by NICE finds a man who they assume to be Merlin, but when he returns with them to NICE, no one is able to communicate with him. They try speaking to him in Latin, which they assume Merlin would understand since he comes from a time when Latin was widely spoken by the educated, but he gives no response. As it turns out, the reason the supposed Merlin can't understand what they are saying in Latin is that he isn't really Merlin at all but an old tramp that the real Merlin has placed under a spell and left in his place.
Meanwhile, the real Merlin meets Ransom, who gains credibility with Merlin by revealing that he--like Merlin, apparently--can speak the Old Solar language. Ransom tells Merlin that "it is long since it has been heard. Not even in Numinor was it heard in the streets" (p. 272)--referring to a kingdom which appears in Tolkien's The Lord of the Rings. Merlin ends up joining forces with Ransom and his associates in their quest to defeat NICE. Merlin is sent to NICE in the guise of a Catholic priest with a knowledge of an ancient language Merlin would have known. The supposed priest (the real Merlin) is "forced" to accompany the false Merlin (the tramp) as his interpreter during a tour of NICE. During a subsequent banquet, Merlin (or some power working through him) places "the curse of Babel" on the attendees, so that their ability to communicate in meaningful human language is taken away (the book's title derives from an old poem about the Tower of Babel). Chaos ensues, leading ultimately to the destruction of NICE. (Merlin and the tramp, however, escape.)
In short, language--human and otherworldly--is a significant, recurring theme throughout Lewis' space trilogy--one of many important themes in the series. My hope is that my exploration of this topic will pique the interest of those of my readers who have yet to read the books, which are among my own personal favorites.
Image of C.S. Lewis from Wikimedia Commons