The Halloween we know today—a holiday in which fun-seekers don costumes, knock on strangers’ doors for candy and embrace all things spooky—was born out of ancient traditions meant to appease the dead. Historians say Halloween, celebrated every year on Oct. 31, is linked to the old Celtic festival Samhain, which marked the end of the harvest season and the start of winter. People began dressing in costumes to disguise themselves from spirits, whom they believed came back to life to kill their crops. They also went door to door to ask for food and “soul cakes” to offer the ghouls in exchange for mercy. Watch the video above to learn more.