The Ultimate Discourse About Gildor

[William Cloud Hicklin]

Ok, at http://sindanorie.lima-city.de/RS&TI&WR.htm there's more info than my feeble linguistic ability can absorb (note at the bottom of the page). In pertinent part, we learn that

At the same time {i.e. the Gnomish Lexicon] -ion is the genitive plural of consonantal nouns, e.g. glôr 'gold' > glorion....

By the time of The Etymologies Noldorin, Ilkorin and Doriathrin are the languages of the Celtic branch. Both -on and -ion occur as agentive suffixes, as in #faron 'hunter' (SPAR-), Dúrion/durion 'a Dark-elf' (DOƷ-, DÔ-, MOR-) or else form names as Mirion 'ordinary N name of the Silevril (Silmarilli)' (MIR-), Gelion 'merry singer', also a river (GYEL-). Probably associated with this is the patronymic suffix -ion < YŌ, YON- 'son'.......

There's also Erchamion, expressly Noldorin (=Ilk Ermabuin).

But only in part. There's much, much more. Through all of Tolkien's *constant* changes of mind I think what I've learned is that Tolkien happened to like the sound of -on, -ion as an ending, and then had to explain all the different ways he used it! There is also a whole stack of geographical -ions: Eregion, Dorwinion, Dorthonion, Erydwethion, etc.