Dill Pickles?

A pickled cucumber is commonly called a pickle.
A pickled egg is commonly called a pickled egg.
A pickled olive is commonly called an olive.

It's amazing!
Why is it so?
I don't know.

I had some dill pickles the other day and there wasn't any dill in the pickle jar.
They pickled the cucumbers without any dill spice and still labled the jar dill pickles!

Sorry, but I just don't get it. Dill pickles?