Invite, but never command, friendly spirits, faeries, or elementals to join you as you wish. In some traditions it is common to invite ancestors to join you, especially during the dark days from Samhain to Imbolg when it is believed that the portal between our dimensions is at its thinnest.
Source: wiktionary
The root word takes us back to the ancient Celts who held a ceremony called Samhain in order to honor the harvest cycle. Each October 31, the harvest would end, and the Irish would gather to kill livestock. Often, they would throw the animal’s bones onto a roaring bonfire. The people who attended Samhain believed that the dead made their presence known during the festival, and that they must be appeased or else they would cause trouble and hardship for the townspeople.
Source: wiktionary