The Oxford English Dictionary traces the word "evolution- to seventeenth-century English poetry. Here is the word's key meaning "the sequential exposure of prepackaged potential "inspired the first recorded usages in our language. (324).
One reason for the shift in definition lies with Darwin's contemporaries. .
a great majority of his contemporaries, while granting the overwhelming evidence for evolution's factuality, could not accept Darwin's radical views about the causes and patterns of biological change. Most important, they could not bear to surrender the comforting and traditional view that human consciousness must represent a predictable (if not a divinely intended) summit of biological existence. If scientific discoveries enjoined an evolutionary reading of human superiority, then one must bow to the evidence. But Darwin's contemporaries (and many people today as well) would not surrender their traditional view of human domination, and therefore could conceptualize genealogical transmutation only as a process defined by predictable progress toward a human acme (326).
I think that reasoning behind his contemporaries not wanting to accept his ideas also lies in their own jealousy. Darwin introduced one of the most important concepts ever. They probably wished they had come up with it first. Instead of accepting his ideals and revolutionary concepts, they rejected them and mislabeled his process deliberately. It was the egocentric views of such contemporaries as Herbert Spencer that led to the establishing of "evolution- as the general name for Darwin's process. "Spencer held a dominating status as Victorian pundit and grand panjandrum of nearly everything conceptual (326)- and instead of realizing the magnitude of Darwin's process he decided to chastise it by purposely misrepresenting it.
Another reason for the shift in definition is that in most cases, people don't reject the concept of evolution because they disagree with the science.