Why do so many Of the Final Fantasy games have someone named Cid?Is there a backstory to the name?

It's just some sort of... well, I don't want to say Running Gag, but close.
Just like the summons Ifrit, Shiva etc, and the ocassionally Biggs & Wedge characters, Cid is a typical Final Fantasy element. He's been in all games starting with 2, I believe, but correct me if I am wrong, and almsot always he has to do with airships.

That's all there is to it. These Cids are definitely different Cids, just like the games are set in different worlds. They have sometimes extremely different personalities. Just compare FFVII-Cid to FFVIII-Cid. :)