a child whose accomplishments or other attributes are used by the parents to impress others
The star athlete became the trophy child for the stepfather.
1510s, "a spoil or prize of war," from Middle French trophée (15c.) from Latin trophaeum "a sign of victory, monument," originally tropaeum, from Greek tropaion "monument of an enemy's defeat," noun use of neuter of adjective tropaios "of defeat," from trope "a rout," originally "a turning" (of the enemy); see trope. Figurative extension to any token or memorial of victory is first recorded 1560s. Trophy wife attested by 1984.
[fr the action of fishing by trolling]