It's more about linguistic structure than origin of words.
Kannada, Telugu & Malayalam, even pre-dravidan-movement Tamil have lot of borrowed sanskrit vocabulary, but they retain structure of Dravidian languages.
Also most common words used are also Dravidan origin.
Another small thing unique about Dravidian languages is clusivity, there's exclusive 'we' and inclusive 'we'. While modern Kannada, unlike Tamil / Telugu, doesn't retain this feature, some dialects such as Havyaka retain this feature.
Kannada, Telugu & Malayalam, even pre-dravidan-movement Tamil have lot of borrowed sanskrit vocabulary, but they retain structure of Dravidian languages.
Also most common words used are also Dravidan origin.
For example:
Kannada - Naanu, Tamil - Naan, Telugu - Nenu, Malayalam - Njan
Etc..
Another small thing unique about Dravidian languages is clusivity, there's exclusive 'we' and inclusive 'we'. While modern Kannada, unlike Tamil / Telugu, doesn't retain this feature, some dialects such as Havyaka retain this feature.