Samhain, pronounced as "sow-in," is an ancient Irish festival that marks the end of the harvest season and the onset of winter. Celebrated from the evening of October 31st to November 1st, Samhain is considered one of the four Gaelic seasonal festivals, alongside Imbolc, Bealtaine, and Lughnasadh. It is widely recognised as the precursor to modern-day Halloween.

The origins of Samhain can be traced back over 2,000 years to the Celtic people of Ireland. It was a time when the boundary between the living and the dead was believed to be at its thinnest, allowing spirits to roam the earth. This belief led to various customs and rituals aimed at appeasing these spirits, which included offerings of food and drink, as well as lighting bonfires to guide the souls of the deceased.

During Samhain, it was customary for people to don costumes, often made from animal skins, to disguise themselves from evil spirits. This practice of wearing costumes has evolved over the centuries and is a defining feature of contemporary Halloween celebrations.

As you can see, Halloween as we know it today has its roots firmly set in the Irish Festival Samhain.