Meaning

noun a person who pleads for a cause or propounds an idea

noun someone who expounds and interprets or explains

noun a mathematical notation indicating the number of times a quantity is multiplied by itself

originFrom Latin expōnēns, present participle of expōnō (“to expose; to exhibit, display, set out; to explain”), from ex- (“out, away”) + pōnō (“to lay, place, put”).

Etymology from Wiktionary, CC BY-SA 3.0