Name suffixes/prefixes in Middle-earth

Question

I know that there are some things in languages of Middle-earth that name someone the son or daughter of another, for instance Thranduilion meaning son of Thranduil. What language is that specific one? Perhaps Sindarin? And how would it be applied to other names? For example, would son of Oropher be Oropherion?

Answer 1

The construction is actually Quenyan; -ion is the male patronymic suffix:

[Quenya Lexicon] gives yo, yond- as poetic words for 'son', adding: 'but very common is -ion in patronymics (and hence practically = "descendant")

^{_{History of Middle-earth II The Book of Lost Tales Part 2 Appendix: "Names in the Lost Tales Part 2"}}

At least one other example (along with some more usage) is given later:

The 'names of insight' were more often given in the early days of the Eldar, and in that time they came more readily into public use, because it was then still the custom for the father-name of a son to be a modification of the father's name (as Finwë' I Curufinwë) or a patronymic (as Finwion 'son of Finwë).

^{_{History of Middle-earth X Morgoth's Ring Part 2: The Second Phase Chapter 3: "Laws and Customs Among the Eldar" Of Naming}}

I'm unable to find any father-names based on "Oropher", but did find one based on the name "Inglor":

'I am Gildor, [...] Gildor Inglorion of the House of Finrod. We are Exiles, and most of our kindred have long ago departed and we too are now only tarrying here a while, ere we return over the Great Sea.'

^{_{Fellowship of the Ring Book 1 Chapter 3: "Three is Company"}}

Gildor's ancestry isn't a cut-and-dry issue, but the Legendarium has almost always had a character who can be called "Inglor", of the house of Finrod.

Based on the -r suffix alone, I would speculate that "Son of Oropher" would indeed be constructed as "Oropherion", but I have no firmer evidence.

Answer 2

Another example is in the names of the kings of Arnor:

After Malvegil, the Kings at Fornost again claimed lordship over the whole of Arnor, and took names with the prefix ar(a) in token of this.

(from a footnote in Appendix A).