Which term derives from a greek word meaning “to speak with good words” and involves substituting a more pleasant, less objectionable way of saying something for a blunt or more direct way?

   Euphemism

Explanation:  Euphemism is a word that has a Greek root and means to replace some unpleasant or shameful word or expression with some milder, indirect expression or word. It is used instead of some harsh expression, most often, say, to replace the term dead, and so used passed away. However, sometimes it is not a good idea to use a euphemism to mitigate or mask the seriousness of the problem, such as when you say social drinker instead of  alcoholic.