English /p/ in "up" and "open"

From: Rasmus Underbjerg Pinnerup
Message: 36089
Date: 2005-01-31

Dear Cybalist-members

I apologize in advance if this question is trivial, but I tried a
number of lexicons and other ressources and have not been able to find
an answer.

The issue is the /p/ in the English word "up" (and in "open") - it
allegedly goes back to PIE *upo-, but by way of Grimm's Law it should
have become /f/ - and I can't seem to find any answer to why it
hasn't.

The /p/ appears in most other Germanic languages as well (with the
exception of those who have gone through the high german sound shift,
who have /f/). Old Norse has /upp/, Gothic /iup/. Old English also now
and then displays two p's. Could it have been a PIE geminate? Are
there such things - and are they exempt from Grimm's Law?

--
Venlig hilsen / Sincerely
Rasmus Underbjerg Pinnerup
<http://home1.inet.tele.dk/hobbes/>