Arabarra, that's exactly that the kind of explanation I was looking for, thanks! It seems very logical and plausible to me, and as you say, even if it's not the real origin it's beautiful anyway.
About the "bihotza" one, I read that on some web page (can't remember where exactly) so I don't know if it's true either, but I hope so because it's a really nice one.
Well, although I don't know much about the technicalities of grammar, I was reading the Wikipedia article about Basque verbs and I found it really interesting that when they were examining and stripping down words, the actual root was just one letter, which made me that think that every consonant and vowel sound in isolation must have its own meaning... Anyway, I stumbled across another web page yesterday, "EUSKARAREN JATORRIAREN"
and it seems that it's true! (Okay, this might not be such an amazing thing for people who know about linguistics and stuff, but at least for me it is
). Here's what it says about the consonants B, D and G (including my bad English translation for those who don't speak Spanish):
1) B.- Significa la parte baja de los lugares y objetos. Su contenido depende de la vocal que le acompaña (Ba-tu, Be-tu, Bi-tu, Bo-ro, Bu-ru). (Means the lower part of places and objects, its content depends on the vowel that accompanies it.)
2) D.- Significa pendiente de arriba abajo (Da-za, Deza, Di-ma, I-Do-eta, a-Da-rra, u-Da, u-Da-la). Su contenido depende de la vocal que le acompaña. (Means hanging downwards [I think], its content depends on the vowel that accompanies it.)
3) G.- Significa la parte de arriba de lugares y objetos. El contenido depende de la vocal (Go-i, Go-ra, Ga-i-na) (Means the upper part of places and objects, its content depends on the vowel that accompanies it.)
...it's a really interesting page.