Vincent is right about Zelda being a Legend. Link is legendary Hero and Zelda is of course the Princess of Hyrule. By this I talk about the very first zelda and Link.
She is also in Oracle of Ages. These are just returning characters in the whole Zelda series. Maybe they are named after their ancestors but to me it doesn't bother me at all.
In OoT we don't know if Zelda's mother was also called Zelda and there has never been said there were more Impa's. In ST Zelda does refer to her grandmom Tetra who was Zelda. And it was normal in those days to name children after their ancestors. And in Impa's her case they all talk about the...