I'm trying to translate my name into Sindarin (which is the elf language I prefer). I've chosen a fancier interpretation "Watchman" (versus it's truer meaning, "watchful" which would just be Tirith, unfortunately).
So how does Tirith + dîr combine? Does it remain Tir + dîr?
If I had to guess, I'd say tirith + dîr would simply result in Tirithdir, given that thd is an attested cluster (at least in Noldorin). Tirdir should also be fine.
If memory serves there was a suffix that meant "one who" or something; do you know what suffix I'm referring to? Would that make more sense? I suppose that would require the "Tir" prefix since Tirith means "watchful/vigilant"
Are you talking about -ron? That would give you Tirron Guard/Watcher (Male). Tiror would be gender neutral.