Well there are two roots I found for "rhin": the Welsh root means "secret" ( which is kinda cool) and the Greek word means... "nose." Hope that helps!

According to Wikipedia, don is also a suffix that can mean tooth, which sounds a little more battle-ready than nose.

I was looking at the Wikipedia page for Wagner's Ring cycle yesterday because I know that Lewis was a huge fan of it, and saw something that might be related to this topic: the first drama in that cycle is called Das Rheingold, translated as The Rhinegold, which refers to the gold stolen from water-sprites in the river Rhine and used to fashion the eponymous ring. It seems like there might be a bit of a link there.

As an aside, Lewis seemed to like names starting with Rh: we also see the characters Rhince and Rhoop in VDT.

Perhaps the name was linked to an adventure in the Golden Age of Narnia that we do not have knowledge of, or perhaps Peter named his sword shortly after the battle with the Wolf. What do you think?

I would lean towards the former, but the way Peter tells us the name and then says "with it I killed the Wolf" — as though killing the wolf is connected to the name — makes me think it must be the latter. If the name Rhindon had originated from some other adventure, you'd think he would have referenced that, too. I think my general vibe is that it was a name he gave the sword himself, not with a particular meaning, but because he liked the name.

If the name Rhindon had originated from some other adventure, you'd think he would have referenced that, too.

To be fair, I think Lewis wanted to reference something readers would recognize from The Lion, the Witch and the Wardrobe.

Posted by: @rose

I would lean towards the former, but the way Peter tells us the name and then says "with it I killed the Wolf" — as though killing the wolf is connected to the name — makes me think it must be the latter. If the name Rhindon had originated from some other adventure, you'd think he would have referenced that, too.

I agree. Peter solely remembers that battle with the wolf as connected with his sword somehow. It may mean "with it I killed the wolf" because that was his first battle with it and he may have named it after a language that the Narnians have. In Beaver's First Names?  some people were talking about the Narnians having their own language. If the Narnians had their own language maybe Peter named Rhindon after that?

I also think that Peter may have been just referencing the first battle using Rhindon against the wolf because it was his first Battle. I think that Peter may have named Rhindon in the Golden age to show the specialty that he has for the sword that Father Christmas gave him on his first time to Narnia. He would've named it in the Golden age because then he has used Rhindon more and had a special connection with the sword.