Well, I'm actually a French speaker and what makes me say that is the "a" in happiness that is IMO never going to be pronounced by a French speaker the same way as the "a" in "a penis".

The "e" might get pronounced as the "I" in penis by a good enough English speaker, but probably not by a bad English speaker.

I also believe that stress would be totally different, put only on the "a" by a French speaker.