Last translation assistance request for a while, thanks to Ellanto for contributing to my understanding of Sindarin so far this Yule season. I read Gil-Galad was born Ereinion "Scion of Kings", and thought to use the plural "erein" = "kings" for something like Ereintir the "Kings Guard" or "Watcher of Kings".
Does that work in proper Sindarin(or even what we know of Noldorin) for a given name, or could you not shorten "tirith" which translates as "watcher, guard, protector to "tir" and use it as a suffix in Sindarin? Would that only work in Quenya as seen in Palantir? I've seen tirith and tir translated interchangeably into Sindarin/Noldorin but that could be due to old sources I'm just not sure.