So what’s the name of Arwen’s sword, Gwemegil or Hadhathang? We got this info from a reliable source in the world of Elvish linguistics:

“Decipher did not have a name for Arwen’s sword from New Line, and was going to make one up; the name they had come up with didn’t mean what they thought it did. I supplied “Gwemegil”. I cannot
speak for Decipher vis-a-vis their relationship with New Line regarding this sort of thing, but if “Hadhathang” is what David Salo had the propmeisters inscribe on the sword, then that is its name. “Gwemegil” just means “maiden-sword,” so perhaps it can be taken as a description rather than a name.”