Definition:
The term "apple of discord" originates from classical mythology. It refers to a golden apple that was thrown into a banquet of gods by Eris, the goddess of discord, who was not invited. The apple had the words "for the fairest" written on it, which led to a dispute among the goddesses Hera, Athena, and Aphrodite. Paris, a prince of Troy, ultimately awarded the apple to Aphrodite, which set off a series of events leading to the Trojan War.
The phrase "apple of discord" describes anything that causes disagreement or conflict. It has roots in mythology but is used in everyday language to highlight disputes or contentious issues.