When it comes to the realm of Elvish names, two questions top the list of Most Frequently Asked:
How do I make a name that means X?
What is the meaning of name Y?
Question one is arguably the easier of the two to answer. With a working knowledge of Quenya or Sindarin, it's easy enough to make names with any meaning from Shining Moon to Oily Dog. Most of the time, queries of the 'I want a name that means...' variety can be answered simply.
Question two, on the other hand, can be tricky. For every certain name meaning that Tolkien provided, he left another gaping hole elsewhere. We're certain of Elrond, Galadriel, Celeborn, and Glorfindel, but others are far dodgier. On top of that, some of the meanings given in Peoples of Middle-Earth are just plain silly.
Yes, I dared say it. PoME is weird. Not only because the explanation of some names given therein makes no sense whatsoever, but also because it contradicts a previous (sensible) explanation from Lost Tales. Here's how.
In PoME text The Shibboleth of Fëanor, we're told that the name Finwë will have no particular meaning, because Finwë himself had no specific connexion with the Quenya word fin (hair). Not only does this make little sense, but it also contradicts a previous (sensible) discussion of this name. A look at Book of Lost Tales 1 (p 253) will give a different explanation:
As a proper name this is not in the dictionaries, but GL gives a common noun finweg 'craftsman, man of skill' (with fim 'clever; right hand' and other related words); for -weg see Bronweg. In QL derivatives of root FINI are finwa 'sagacious', finie, finde 'cunning'.
The GL and QL listed above are, respectively, Gnomish Lexicon (published in Parma Eldalamberon 11) and Qenya Lexicon (Parma Eldalamberon 12).
At the time Tolkien created the name Finwë, the Fin- root had nothing to do with hair at all. Rather, it meant 'cunning' or 'skill': both words that are far more aptly applied to the Noldor and fitting for their King. The roots for 'hair', at this point, as listed in QL, were FILI and FIRI, and out of the question when it comes to finding a meaning for Finwë's name.
With Finwë sorted, it's safe to say that these three names likewise have nothing to do with hair (and nor do any of the other Finwës: Curufinwë , Nolofinwë, Arafinwë, etc.). Fingon is done a particularly bad disservice in PoME, where his name is translated as the nonsensical 'Hair Shout'. Personally, I find this worse than 'Oily Dog'. The Fin pattern of naming makes it clear that all of these descendants were named after their famous father/grandfather/great-grandfather, meaning the Fin here has no more to do with hair than does in Finwe's name. Literally, Findekáno would be composed of the elements finde (cunning, as above) and káno (commander), while Findaráto would be finde and aráto (nobleman). OR one can assume that the Fin- is merely patronymic, in which case the name would be 'commander descendant of Finwë' and 'noble descendant of Finwë'.
The same Fin- meaning would apply to all of Finwë's thusly-named descendants: Findis, Finvain, Finbor, Findor, and so on.
Unfortunately, unlike Finwe, I've been unable to find anything concrete on this name. But if we go on the assumption that the explanation given in PoME (meaningless similarity to olba: 'branch') is as correct as that for Finwe, there has to be a better meaning for Olwe out there. One possibility from the QL is the word 'ole' (from root OLO 1), meaning 'three', to signify the third of the Kings of Valinor. However, this is only a guess on my part.
This name is listed straight out in the QL: Qenya Aikaldamor, meaning 'broad shoulders'.
The latest versions of Quenya list the verb mahta-, 'to wield a sword', but a better relationship might be found with the old QL word maha (hand), giving a rough meaning of 'person who works with his hands'.
The original version of his name is Dairon, which seems to be linked to the Goldogrin verb daira-, 'to play'. So, 'Player'. From BoLT2 (p 10):
Dairon was then a boy strong and merry, and above all things he delighted to play upon a pipe of reeds or other woodland instruments, and he is named now among the three most magic players of the Elves.
Under the root RESE in the QL, we have two possibilities: the verb resta- 'to aid, support, help, rescue', and the noun reste, meaning 'kin' or 'kinship'. These give several possibilities. The first, owing to Erestor's original incarnation as a kinsman of Elrond, is the simple meaning 'kinsman' from reste. Another, more appropriate to his later role in LotR, would be 'aide' or 'helper' from resta-.
BoLT1 (p 265) says:
This name is not found in either dictionary, but seems likely to be connected with words given in GL: rû and rûm 'secret, mystery', ruim 'secret, mysterious', rui 'whisper', ruitha 'to whisper'.
A meaning along these lines is appropriate for Rúmil of Tirion, but could also be applied to the Third Age Rúmil, as that name was borrowed outright from the earlier works.
Linguistic Foolery:: Answers from Old Sources: What Does That Name Mean?
© Darth Fingon
http://www.silmarillionwritersguild.org/reference/linguistic_foolery/name_answers.php