from The American Heritage® Dictionary of the English Language, 4th Edition
- n. A yellow-colored card shown by a referee to a player, especially in soccer, to indicate that the player has committed a flagrant foul. Being shown two yellow cards results in ejection from the game.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. a yellow-coloured card, shown to a player, (especially in association football), as a caution that he has committed a flagrant foul; a further such foul would result in a red card.
Sorry, no etymologies found.
However, Edinburgh raised their game and Leinster, conquered by Toulouse last weekend, looked tired as great hands from Nick De Luca got his side on the attack and Heaslip was flashed a yellow card for a deliberate knock on.