Latin testu:do and tortuca

From: Joao
Message: 35698
Date: 2004-12-28

Does anybody know the etymology of Latin testu:do: (-inis) "turtle" ? It seems to be related to testa, but what's the analysis? What is the meaning of the suffix.
 
Neo-Latin derivatives, tortuga, tortue, and English tortoise and turtle came from a Latin *tortuca? What's its origin? Portuguese has tartaruga, which usually analysed as corruption of tortuga, or from an odd Greek tartaroukhos "Hells's Guardian". What is the current view.
 
Portuguese has a name for terrestrial turtles, ca´gado (in Brazil we also use jabuti, of Amerindian origin), which would come from Latin *cacitus or *cacabatus. Any idea?
 
 
Joao SL