Final answer:
Dressing up in costumes on Halloween originates from ancient Celtic traditions. It was thought that disguises could fool harmful spirits wandering the earth. This tradition carried over into present-day Halloween celebrations.
Step-by-step explanation:
One reason why we might dress up in costumes on Halloween today can be traced back to ancient Celtic festivals. During these, people would wear costumes and masks to disguise themselves from malicious spirits believed to wander the earth on the eve of their New Year, which coincidentally fell on October 31. This tradition was later integrated into Christian practices, and over time, evolved into the fun and often spooky costume tradition we recognize today during Halloween festivities.
Learn more about Halloween traditions