Proto-Indo-European (PIE) is a linguistics-divined language based on common words in current and past European languages. It is linguists' best guess as to what was the first (proto) language spoken by the earliest Europeans who migrated from their supposed original roots in Africa. Using common words found in most languages, linguists have put together this proposed language. It is a very compelling idea. It is oddly and, in my opinion, inappropriately, used by modern neo-Nazi groups.
In the 1700's European colonization brought a class of learned mangers, clerks, dignitaries and leaders to previously unexplored regions. These highly educated people were needed tor the running of the various colonies established by England, France, Spain, the Netherlands, etc... Many of them were educated in modern and ancient languages, a perfect job requirement for their duties in the New Worlds. In particular, William Jones (1746 – 1794), who served as a judge in Calcutta, became proficient in Sanskrit and made the Gestalt Aha! concerning the similarities in languages.
Grimm Brothers - Jacob & Wilhelm Grimm
Grimm's Law - Indo-European-Languages
Grimm Scholarship: The First Sound Shift
JONES, WILLIAM, Sir
Indo-European language dictionary