Pep — это сокращение слова pepper. Где-то с середины 19-го века его использовали в значении "энтузиазм, бодрость духа".
▪️Before the big game, the coach gave the team a pep talk to boost their confidence and motivate them to perform at their best.
▪️I can’t believe how much her pep talk helped me; I went into the interview feeling like I could conquer anything.