Vanpir was made up by an unnamed German officer in 1776. He used the word to mean werewolf.
During that year there were thousands of reports that the plague that was running wild in the Slavic regions was started by revenants. These revenants were werewolves in life, but rose from the dead to be what was locally called Vrykolakan (a vampire).
The German officer changed the word vrykolakia to one it’s said he made up the word Vanpir. He never shared the reason for the change.
Newspapers started to use the word in their stories. They French stared using Vampyre. Those stories crossed the channel to England. The British changed the word again to fit their audience. And we know have the word Vampire.