The ugly Christmas sweater trend started back in the 1980s when people began embracing the tacky and garish aspects of traditional holiday sweaters. The sweaters often feature bright colors, bold patterns, and festive designs like snowmen, reindeer, and other holiday icons. The trend became even more popular in the 1990s when celebrities began sporting the sweaters at holiday parties, and it has continued to gain popularity in recent years as people enjoy the humorous and ironic aspect of these eye-catching sweaters.