A couple of things:
The name Kagome comes from a Japanese children's game. As far as I knew the word was nonsensical. I of course could be wrong.
As for Inu-Yasha's name (Gods I wish I remembered what book this was, some official guide to the series):
I believe in either the Chinese or the Hindu beliefs there was a god called Yaksa, who was evil. As Buddhism spread East, to Japan, Yaksa took on a more benevolent personality. In his final incarnation in Japan, the name became Yasha and he represented the balance of both the good and evil aspects of his personality. Thus when Takahashi Sama chose the name for the dog-boy of her comic, this seemed the natural choice, as Inu-Yasha eventually has to come to terms with his human and demonic heritage.
This is what I read about that.
As for DBZ, the Saijins are named after foods, Bulma and her family are named after underwear, and the Nameks are named after snails for the most part. And allegedly, ChiChi means breasts. xp I think this personally extended from Toriyama San's laziness. whee