Americans love accusing others of plagiarism and shaking their finger. In my mind, the words must have some kind of special meaning. I am not sure anything taken out of a minor league political speech written by someone other than the person who delivers the speech can ever qualify as genuine plagiarism.
There is no telling who first said things like”let your word be your bond”……….followed by the standard verbiage that follows. This stuff shows up in countless political speeches as well as in numerous graduation speeches.
I trace that generic speech speak back to P.T. Barnum. It is part of his autobiography as well as another biography that is almost identical.
For words that are spoken over and over throughout history, to give credit it would be impossible to find where the words actually originated. I walked outside today and said, “it sure is hot today, but that is Texas. To whom should I give credit?