goodwill ambassador

noun

Etymology: Origin 1927 when Calvin Coolidge, the United States president designated Col. Charles Lindbergh its Goodwill Ambassador during one of his most famous flights. As a compound word representing an honorific title that was merged over time from three lexemes good-will plus ambassador which is still used descriptively by the State of Kentucky to define the Kentucky Colonel as its "ambassador of good-will".

1. A public figure who, as a volunteer, is an advocate for a good cause on behalf of a public organization.

   “Russian supermodel and philanthropist Natalia Vodianova became a United Nations goodwill ambassador on Wednesday, pledging to promote the sexual and reproductive rights of women and girls and tackle stigmas surrounding their bodies.”