Oh dear, still excited aren't we. Okay, there are major differences between families adapting to new climes, new languages, new environs and the rape and plunder of smaller, 'lesser' cultures and languages by those who care not a whit for how the people thus affronted might feel on the matter. Yes, language changes over time. No, it doesn't need rank amateurs whipping it on.
I've got no problem with you asking the question which is why I bothered to answered it correctly. I can even patiently tell you that while the close Annwn/Annwfn does indeed mean, as posted, 'the underworld, hell' that equally close is Annwyl which means 'beloved, dear' and if it would help, can tell you how to pronounce them. I'll also nicely tidy up your sentiments into...
There is no shame in not knowing, there is only shame in not finding out. - Chinese proverb
A motto I agree with wholeheartedly.
However, I'm getting a tad impatient with the reaction to precisely what you sought. You clearly had some instinctive concern about changing the name willy-nilly like that and definitely I think it would be wrong and in response to your query, said so. If you don't like that, oh well.
And now you want un-serious. Did you come here and post expecting that we would have a bit of a giggle, type down anything silly we could think of and flitter off to run in the sprinklers or that we take your query seriously, do serious research and give you a serious answer? We do the latter. Well, usually. Sometimes we slip into fecitiousness and the occasional hiccup of sarcasm ;o)