Well, I'm not Welsh either, but I live in Wales, and I'm a postgraduate student studying medieval Celtic personal names. I keep an eye on the modern scene as well out of curiosity, and I've never come across an Adara
, male or female, nor is the name listed in any modern Welsh baby name books (although Aderyn 'bird' is). I did go to school with an Adara
(England), but she was English, and knew that her parents had chosen a Hebrew name. There are a number of sites claiming to list Welsh names - it's best only to trust those that are collated and run by Welsh speakers living in Wales (of which I believe there are none - Welsh name websites that is). Name websites tend to fall prey to the fear that they may be missing something if they do not include every name that has even only a vague suggestion of the appropriate ethnic origin. Then other sites collect from them and the whole thing goes round in an increasingly inaccurate circle...basically, don't believe anything you read on a website until you've checked it with a more reliable source :).
I substituted Afaon for Avaon because there is no v in Welsh; f represents the v sound, and ff stands for the f sound. No Welsh speaker would ever spell a Welsh name with a v. Avaon is also not a name I have ever encountered in modern Welsh usage, but the name does ring a bell - I'll have a look tomorrow and see if it turns up in my databases anywhere - I suspect it appears in the Four Branches (Welsh mythology) somewhere.
THe question about the sci-fi novels was because two of the three names you were discussing were a little odd (more nearly Welsh than actually Welsh), and the sort of name that turns up in pseudo-Celtic sci-fi, but as you picked up the names from websites, it's more likely that I should be asking the creators of the websites about their reading tastes.
I'm sorry for my short reply before; I assumed you knew more about Welsh things...