Every word in the german language that contains the particle "zeug" expresses something that is with something in some sense or the other. Sometimes in a weird sense.
You could use it as a noun, a verb, a whatever. "Das Zeug" means "stuff", as in the stuff that's with you, in every stretched semantic the word "with" could be used. Stuff that belongs to you, stuff that you take with you, stuff that you point to, stuff that you talk about...
... If that product was your journeyman's piece, you may now enframe your Zeugnis, which came to pass because someone bezeugte, that he was there with you when you created it and
Babies are created when a man lies with a woman, therefore doing it is called "zeugen". If you were there with them, hidden, watching that, you could testify ("bezeugen") that them both have been in the act of impregnating her ("Zeugung").
(Found in a 4 year old forgotten file in my home directory, source unknown)