Trisavo or Trisavolo?

My first posting on the naming convention for Italian ancestors has been corrected, thanks to a great catch by Francesco.

I had confounded the Italian words avo and avolo, which are synonymous and mean grandfather. Of course, nonno mean grandfather. When multiplicative prefix is attached to any of these roots (avo, avolo, nonno), the number of generations is extended. Thus, avo means grandfather, bisavo means great grandfather, trisavo means great great grandfather, etc.

Avo is derived from the Latin word avus and avolo is derived from the Latin diminutive of avus, avulus. Interestingly, the English uncle derives from the same root via the intermediate Latin word avunculus (maternal uncle).

Technically, bisavo, bisavolo, and bisnonno are all correct and proper words. However, the frequency of usage seems to vary by degree to ancestry. In practice, bisavo and bisnonno seem to be much more commonly used than bisavolo whereas trisavolo seems to be much more common than trisavo or trisnonno.

A further complication comes from the fact that in the plural, which is the example I originally provided, the -avi form seems to be written into Italian law where bisavolo is used instead of bisavo or bisnonno.

I know I've made this more confusing than I meant to, but the long and short of it is that different Italians will probably use slightly different (but correct) words for their ancestors. But the most popular constructions seem to be:

1. il padre (i genitori)
2. il nonno (i nonni)
3. il bisnonno (i bisnonni)
4. il trisavolo (i trisavi)
5. il quartavolo (i quartavi)
6. il quintavolo (i quintavi)