Traces of Oscan, Umbrian, and Etruscan found in modern Italian, via vulgar Latin

"In many Italian words, the appearance of an Oscan f where Latin has b between vowels indicates that Oscan forms with f must have existed in vulgar Latin speech, even if unrecorded."

- The Story of Latin and the Romance Languages, by Mario Pei

Dead languages pre-existing Latin have had an impact on modern Italian. Here are some examples from the same source to demonstrate this:

1. Latin "scarabeus" and Italian "scarafaggio" (beetle)
2. Latin "bubulcus" and Italian "bifolco" (ploughman)
3. Latin "bubalus" and Italian "bufalo" (wild ox)

Oscan, as well as Umbrian and Etruscan, are non-Indo-European languages that were once spoken in present day Italy. Although Latin became the dominant language of the peninsula, Latin speakers were known to incorporate words from their neighbors; as implied above, Oscan pronunciation influenced vulgar Latin (which was undocumented, the only documented Latin being the "proper" Latin of the elite), which in turn influenced the Italian language that developped out of not-so-"proper" Latin. [On a side note, I would like to explain that I use the word "proper" in parentheses because linguists do not make distinctions between proper and improper use of language. I can get into this another time]. I would assume that other languages native to the region had a similar effect on spoken Italian via it's predacessor, vulgar Latin.

Now please consider the following Latin words:

1. "asinus" (donkey)
2. "caseus" (cheese)

The letter s is not normally used between two vowels in Latin; a letter r would normally be used in such instances (such as a word for ear, "ausis," which Latin speakers turned into "auris"). Because this usage is inconsistant with normal patterns of spoken Latin, linguists have come to presume that such words as "asinus" and "caseus," are not originally Latin (and therefore not originally Indo-European) as one would think, but rather that these words were borrowed from the Oscan or Umbrian neighbors of Latin speakers.

Source: The Story of Latin and the Romance Languages, by Mario Pei