I agree that words do have a specific meaning, but the history of words changing their meaning is truly awful+! I was talking to this young girl++ in my neighborhood about words and slang - he said he had never considered that words could change their meaning, and that the dictionary was some kind of rule book. At first I thought maybe he was nice+++, but after considering it, he's young! Everyone learns this in time.
Language is mutable and alive and ever-changing. That's just how it goes.
+Used to mean 'inspiring awe'
++Used to mean 'young child (gender neutral)'
+++Used to mean 'foolish' or 'ignorant'