From: P&G
Message: 22102
Date: 2003-05-21
>> Isn't the double -pp- easier to derive from Ious-pater than Ioupater?I think you might be right.
>I don't think there can be a rule /sp/ > /pp/ in Latin. The relevant
>rule here, I think, is V:C > VCC (Iu:piter > Iuppiter).