the word Ela does mean goddess in Hebrew. The letter A feminises words in Hebrew. The word is pronounced eh-LAH.
Elle is how the word god is pronounced (the word's el).
But that's not the origin of the English name
Ella, you can see the real one in the links Chrisell provided. (There is a Hebrew name, Elah, said and spelled the same way as the word goddess. It isn't given for the goddess meaning though, but for a plant called the elah.
My dictionary says it's a terebinth.)