lexicostatistic techniques.    From Wordnet, Princeton University. 

15To initiate the lexicostatistic exercise, however, one must first determine whether the words claimed to be inherited from a proto-language are indeed shared retentions of particular old cognates, that is, if they truly stem from a common root that shared a common meaning.    From Wordnik.com.  [Societies, Religion, and History: Central East Tanzanians and the World They Created, c. 200 BCE to 1800 CE] Reference