What does “(jemandem) was vom Pferd erzählen” mean in German?

Teasing her grandmother during this flag-guessing game, the granddaughter jokes ich kann dir ja was vom Pferd erzählen — “I could tell you a tall tale (and you wouldn’t know the difference).” Jemandem was vom Pferd erzählen means to lie to someone or feed them nonsense; if someone says it to you, they’re accusing you of bluffing.

Nobody agrees on where horses got involved: theories point to the Trojan Horse’s famous lie, to nobles literally talking down “from horseback” to less educated listeners, or to horse traders' long history of exaggerating an animal’s age and health to close a sale. Whichever story is true, the phrase survives as a light, everyday way to call out a fib.