Short answers, pulled from the story.
François Louis Ganshof published the book Qu'est-ce que la féodalité in 1944 which became the standard reference for understanding medieval Europe. He described feudalism as a set of reciprocal legal and military obligations revolving around three key concepts: lords, vassals, and fiefs.
The word feudal first appeared in a charter issued by Charles the Fat on the 8th of May 884. Medieval Latin documents used terms like feodum and feudum to describe land grants exchanged for service before the term evolved into its modern meaning.
Elizabeth A. R. Brown published The Tyranny of a Construct in 1974 rejecting feudalism as an anachronism lacking basis in medieval reality. She argued that modern historians read the concept tyrannically back into historical records where it never existed as a formal system.
The French Revolution abolished remnants of the feudal order on the night of the 4th of August 1789 when the National Assembly declared it entirely gone. Scotland maintained residual feudal tenure until the 28th of November 2004 when new legislation entered full force.