Answer: Appositive: the Scoutmaster. Noun or pronoun renamed: Mr. Murray.
Explanation: a word (other than a pronoun) used to identify any of a class of people, places, or things, or to name a particular one of these. An appositive is a noun or noun phrase that gives more information about other noun or pronoun that precedes it. In the given sentence we can see an example of an appositive phrase in the words "the Scoutmaster" and it is giving more information about the noun "Mr. Murray."