It's really hard to come up with good names. I usually use references to anything.
I had an infinity bow and the corresponding arrow for example. Arrow was named "Snow White" and the bow was named "The Huntsman" for example.
I once had a sword which was called "The Slice of Life".
Let's see if someone gets the reference of the latter one. Snow White and The Huntsman should be pretty obvious that's why I just ask for the origin of "The Slice of Life".
A few suggestions:
"Robin Hood's Bow"
"The Cruel Hand of Fate"
"Houston, We Have A Problem"
"Man's Best Friend"
I rarely name my Sword and Bow, only once I named them and that was in a creative world that is a long gone now.
I figured out that since I was the leader and creator of this floating Villager empire, I needed to bring them justice by protecting them. So I named my enchanted Diamond Sword, "The Justice" I named my bow, "Snake`s eye" for no apparent reason.