What are some examples of synecdoche? Is "I give you my word" a synecdoche?
A synecdoche occurs when a thing is referred to by one of its component traits.
Frank Sinatra was a complex man with many distinctive features and traits. He is slangily referred to by arguably the least important of them--"Old Blue Eyes." This is a synecdoche. Similarly, Jimmy Durante was often called "The Shnozzola" (for his outsized nose) and Al Capone was known as "Scarface." "I give you my word" is a bit of a reach. "Synecdoche" is low on the list of terms I might apply to that phrase.